ASNT NDT Handbook Volume 3 Infrared and Thermal Testing

stone at the left corner and stretched The timber and iron shingles, smaller
stone alternating ·with herringbone rubble in cross section, contribute to divide the
- all of them beneath the parget. The loads and to release them on to the main
base of the wall is cooler because of rising supporting structures. Another typology,
damp. Delamination of plaster appears in widespread in structures of the last
infrared thennograms as warmer areas. In decades of the nineteenth century and the
the same building but in the ·western wall beginning of the twentieth century, is
of the main hall, thermograms show that of small vaults made of hollow
thermal anomalies, typical of filled holes terracotta wares and supported by iron
used during the castle construction, as beams with average spacing of 0.8 to 1.2
warmer areas. m (2.6 to 3.9 ft).

In Oratorio Suardi, 'I'rescore, Italy, the Timber laths cover the supporting
masonry is composed of rubble and lin'le structures. Embedded in mortar or sand,
mortar. The parget is completely frescoed. the paving finishes the floors. Paving is
A homogeneous heating was performed to usually made of timber, stone, bricks or
allow the infrared detection of the bond tile, disposed with bonding that is
of the wall (8 October 1999). A convective stretched, herringbone or other. The
heating for 2 h (3500 \tV, distributed on development of floor tiling produced
1500 m3) was applied and the rubble different kinds of patterned tiles with
beneath the parget appeared. The different thermal properties.
preciousness of the surfaCe avoids a
thermal gradient higher than 1.5 Klrl Vaults
(1.5 °C.!rl; 2.7 °F·h-1).
Structural masonry (mortar and bricks or
The structural masonry of the San stone quoins) usually are used as
Michele monastery, Lunate Pozzolo, Italy, supporting structure of vaults1 dome
was also investigated by infr<Hed vaults and domes (cupolas).
thermography. A thermogram ·was
recorded after 1 h of lighting by two Shuttering bricks/stones are used to
flank the basis of the vaults (for about one
lamps of sao ,~, each, disposed 1 Ill third of the height). In fact increasing the
weight of the vault lets it withstand the
(40 in.) from the surface. The average drift better. Because of the different
temperature increase at permanent regime thickness of the structure thermograms
was about +3 K (3 °C ~ 5.4 °F). The bond show a varying temperature from the
of the masonry is detectable in a basis to the apex, at least in almost steady
thermogram as rubble stones despite the state conditions. Transversal metallic
heterogeneous heating of the parget, chains, spanned at the bases of the vaults,
thicker than 30 mm (24 May 1999). help absorb the horizontal thrust.
Another technique to reduce the drift is to
In cases of mixed texture infrared lighten the vaults ·with interlocking pipes
thermography is successfully applied to to form rings of lightweight permanent
localize placement of bricks and stone. At shuttering.
Sant' Abbondio cloister, Como, Italy
(12 May 1999) infrared thermography After the seventeenth century lighter
makes it possible to detect the bricks vaults were built by using panels of reeds
around the arches and beneath the parget nailed on wooden centering. Often
as wanner areas after 20 min of solar frescoes decorated the pmgcts that cover
irradiation. The colder areas correspond to the panels. Thermography makes it
rubble. possible to see the timbering and the
metallic fixtures, at ease during transient
Analysis of Horizontal conditions.
Structures
The largest domes are often made 'With
In the construction pattern the horizontal external iron beam struu ures supporting
structures distribute the loads to the the metallic or timber shell of the bottom
vertical elements. Briefly, they can be face.
classed as follows.
Roofs
Floors (Girders, Shingles, Laths
and Paving) Generally a suitable roof covers the
structure. Timber beams and rafters are
The main supporting structures, with the simplest supporting structure of
larger cross section, <ne the beams or double pitch and hipped roofs. Trusses
girders. Usually the materials are timber, and a third byer of shingles are used in
iron and cast iron. They can be hidden in larger roofs. Additionally, the coating lies
the thickness of the floor or can be on a lath layer. The roof tiles are tht' mmt
external, sometimes with parget or plaster external layers, used to ·withstand the
facing or just a painted surface. weather. Other covering are made of
wooden shingles, disposed with a
multilayer arrangement or slabs of stones

636 Infrared and Thermal Testing

(slate, gneiss or other). lvfetallic plates or Moisture Diffusion and
occasionally vegetable materials such as Water Content
straw can be also found as roofing in
historic buildings. Usually, during The need to repair moisture damage is
refurbishment, one or more insulating secondary only to structural damage
layers or impermeable membrane are when preserving ancient buildings. The
added between the covering and the presence of water in a structure and its
supporting structure to prevent changes of state (solid, liquid, vapor) arc
infiltration and to reduce heat losses. responsible for damage to the building, it~
content~ and its inhabitants. The same
Examples of Structures in Vaults materials can be damaged differently
depending on environmental conditions
and Roofs and especially on the amount of water in
the wall. Concurrent causes are biological
Another example is the vault of San and chemical or are linked to pollution.
rvlichele in Cambianica, Bergamo, Italy.
The thermogram, shown in Fig. 35 was The knowledge of the water content
recorded after 1 h of convective heating within walls is fundamental to the decay
(4000 W over 2500 m'). The ashlars of the analysis. In cold climactic conditions it is
masonry are well defined. Moreover, usually a key factor when temperatures
cracking at the base of the vault is stay below zero for several months.M• In
detectable; three areas; in the white t110se cases, the water volume grows in
squares are cooler because of moisture tile form of frost and generates strength
caused by rain infiltration from the roof ·within the porous wall materials,
(24 October 1997; temperature before the therefore generating cracks in the
structure especially during long and cold
heating 284 K= 11 oc = 52 °Fi relative winters. In temperate climates during
winter, the thermal inertia due to the
humidity 44 percent; average temperature thickness of the ancient walls (more than
0.50 m), prevents frost inside the wall.
286 K = 13 "C =55 "F; background Damage is limited to the surface, 0.03 or
temperature 281 K =8 "C =46 "F). 0.04 m 0 or 2 in.} deep, because of
continual cycles of freezing and thawing.
The irregular texture due to the reeds
beneath the frescoed parget of the vaults An additional issue related to moisture
is recognizable in the infrared damages of the surfaces is the water
thermogram of Fig. 36, taken at Villa transition between the wall and the
Arconati. The darker areas indicate some ~urrounding environment because of
infiltration of water. Very favorable evaporation and dew. The objective of
environmental conditions let these images
be recorded without applying any FIGURE 36. Thermography of vaults of Villa
artificial heating (23 June 1997, air Arconati Castellazzo di Bollate, Italy. Beneath
frescoed parget of vaults there are reeds
temperature 290.8 K =17.6 "C = 63.7 "F, nailed on timber centering, 13 june 1997.
Air temperature 290.8 K (17.6 oc = 63.7 oF),
relative humidity 36 percent). relative humidity 36 percent.
In a passive test on 22 November 1995,

the timber centering of the vault of
Palazzo Peloso-Cepolla, Albenga, Italy, was
detectable in a thermogram as warmer
areas.

In Oratorio Suardi, the infrared images
of the roof revealed different material
covering the ceiling after 2 h of heating
by convection at 3500 W over 1500 m3
(8 October 1999).

FIGURE 35. Ashlars of masonry shown by
thermography of dome vault of San Michele
in Cambianica, Bergamo, Italy, 24 October
1997 after 1 h of convection heating. Air
temperature 284 K(11 "C = 52 "F), relative

humidity 44 percent.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 637

moisture analysis is to find out the Leakage and Infiltration
sources of water and to plan the correct
intervention to dry the walls and save Infiltration of rain or snow may occur
their surfaces. The main paths of ·water where the roof is not well maintained.
coming into building materials are Typical stains may be found on the
(1) from the ground (capillary rising), ceilings (or vaults) on the upper floor. In
(2) by condensation from the air and case of wide infiltration even the walls
(3) from infiltration because of broken nearby may absorb much more water
piping or guttering or leakage from the than the floor itself (depending on the
roof. thickness and the absorption
characteristics of the walls).
Capillary Rising
It is interesting to observe the
Most ancient buildings are affected by the correlation of water staining on the
presence of moisture due to the surface and the actual water content of
absorption of water from the ground. The each point. Such a visual indication is
presence of water in the ground depends important but sometimes misle<Jding. In
on the following: shallow groundwater; fact, it appears suddenly when moisture
impermeable ground layers (such as clay) concentrates but remains after the surface
that prevent rain drainage; proximity of dries out.
rivers, sea, lakes and channels; proximity
of sewage and drainage system failures; Broken pipes cause localized high water
slope of the ground; inadequate (highly concentration: the wall materials soon get
porous, lacking waterproof layers or saturated. Although in many cases the
broken) pavement near the building. extent of the infiltration will not appear
visually and also not close to the failure,
The bases of the walls are the typical infrared images show the extent of its
areas affected by rising damp. It does not spread. Careful analysis is needed.
depend very much on seasonal thermal
changes. Nevertheless, the water content Detection of Moisture in
and its distribution inside the wall may Buildings by
vary depending on the particular source Thermography
supplying the underground moisten
volume. Thermography for the moisture
monitoring of buildings is well
The main characteristic is an almost documented in the Jiterature.67-n9
horizontal frontier, bending higher from
the ground at the corners or where the Different approaches have been proposed,
masonry is thicker. The height of the imposing a transient thermal state or
damp areas may vary during the year. Salt considering almost stationary the
efflorescence is frequently generated at boundary conditions. Active or passive
the border of the damp areas. techniques have been based on the
changing of thermal parameters70 or using
Water Condensation dependency of optical surface properties
from moistureJl
\'\1here relative humidity is high and
temperature drops, vapor condenses on Generally speaking, the choice of the
the colder surfaces. The condensation risk right time to perform the test is very
depends on a high rate of environmental critical, because various phenomena are
relative humidity and cold surfaces; on activated by the moisture accumulation.
evaporating surfaces, for instance due to a In fact, buildings are subjected to slow
crowd in the rooms; and on inadequate varying but no;sy boundary conditions
ventilation, for instance lack of window and different heat fluxes may interact
frm'nes. with each other in destructive or additive
effects. The building envelope exchanges
Any part of the wall may be affected by energy with the surrounding environment
dew, depending on the temperature of the by convection and radiation. In addition,
wall. Thermal bridges are preferred areas. a significant amount of energy could be
But corners are often subjected to associated with changes of phases of water
condensation because of limited air speed. on the building surface, Hence, a heat and
Condensation may disappear within a mass transfer is activated through the
short space of time and occurs wholE' building envelope, driven by
periodically (in the same season). transient and quasiperiodic boundary
conditions.
The condensation areas often
correspond to stains or mold. The dew The mathematical modeling of the
point may be monitored to measure the thermal problem is very complicat<:'d
wall temperature and relative humidity of because elementary fluxes are combined
the air. with each other. Furthermore, the liquid
and vapor phases are in equilibrium
inside porous material and the phase

638 Infrared and Thermal Testing

changes continuously inside the wall and Of course, using a passive procedure only
on its surfaces. As a consequence, a the environment acts on the surface.
moisture increasing generates warmer or
colder areas than normal one, depending Finally, the following problems may hl'
on the boundary conditions or
gl2'ometrical aspects. A simplified solution anticipated:
is then to be searched, trying to perform
the measurement when transient thermal I. A preliminary scanning of all the
state is more understandable. surface of the wall makes it possible to
set camera parameters and to identi~·y
The final target is to recover from the the most evident anomalies; a set ot
thermogram information about the water further measurements closer to the
content of the surface. The objective of surface yields the actual analysis.
the test could be the evaluation oft he
moisture in each point of the field of 2. Spot heating due to active elements
view. A simpler aim is the segmentation like hot pipelines or electric cables
of the ·whole surface in a few zones of may disturb the test.
more or less homogeneous ".;ater content.
The latter objective is realistic and 3. Dming an active procedure, the
informative. In fact, knowing the water presence of plaster delaminations and
distribution in space, a very few stains or colored parts may affect
measurements made with other methods results.
could be enough. In addition, the wet
areas' location and shapes and their 4. The winter heating aCtive inside the
changes in time are very indicative of the building could prevent a correct
source of the water. As an example, an moisture detection of the wall.
almost horizontal line delimits the wet
zones due to capillary rising. Another key 5. The heating tends to dry the wall
point is the correlation in time between surface, masking the moisture map in
moistened areas extension and the driving case of low to medium water content.
phenomenon. This approach spoils ~he_
imaging features of thermography, hnkmg 6. Thermal bridges and thinner walls, the
thermograms to quantitative measures of imperfect connection between walls,
thennohygrometric conditions. In such a the presence of windows and doors
way, the continuous monitoring in space close to the investigated area -all
given by thermography may be correlated these may cause false alarms.
with the almost continuous data logging
in time of conventional sensors. Surface Evaporation Flux

Infrared thermography can be used for Thermography allows estimation of t11e
moisture evaluation as an indirect evaporation rate of a wall. This technique
technique72 starting from the temperature is based on the high value of the latent
map. heat of water. Each gram of water

An approach in applying evaporating absorbs 2500 J and cools the
thermography is to follow qualitatively
the n:10isture distribution due to the surface ver}' effectively. Therefore, moist
cooling effect of water evaporation.73 areas are colder than dry ones, assuming
Another approach is based on water's high the same boundary conditions. The
thermal capacity revealed during transient appearance of the phenomenon depends
thermal tests?4•7s on air temperature and relative humidity
levels. The flux cp of the evaporating watt'r
A second level is the quantitative is given by Fick's law (Eq. 2) and is
estimation of water content using the proportional to the water concentration
surface temperature distribution in space gradient between the porous surface and
and time or additional measurements the air outside the boundary layer (free
with alternative techniques on selected air):
points. Notice that measuring the water
content of a \Vall by thermography alone (2) <I> t.C
appears practically impossible and an
estimation of the moisture in a shallow -/)-
layer is the maximum achievable result.
t.z
Even if an absolute evaluation of
moisture is possible76•77 a relative At equilibrium, the moist material
approach is much more used. In this case, supplies the water flux, hence <I> is related
the investigation of damp areas is based mainly to the porosity of the material and
on the comparison of the thermal its soluble salts content. The diffusion
behavior of dry areas with damp ones. coefficient D depends on properties of the
Therefore, in the same thermogram there vapor and is a function oft he constant R,
can be both circumstances, assuming the temperature T and the average molecular
same heating and boundary conditions. mobility u of vapor. The measure of <1)
could be obtained, at a specific point,
measuring the relative humidity (lUI) of
the free air and very close the wall
surface. The thickness of the boundary
layer d, where molecular migration takes
plac<:, approximates l1z. i\·lolar
concentration (.'of water can be expressed
as a function of the relative humidity of

Infrastructure and Conservation Applications of Infrared and Thermal Testing 639

the air. Therefore, the flux Q> can be 2. Environmental conditions should
expressed directly in terms of the relative have a medium to high transpiration
humidity gradient (RJ-!1 to RHa) as follows: (relative humidity lower then. XO
percent and air tt>mperature not below
(3)
279 K !6 <>c = 43 oF] in the air surface
where: C~Jt is the molar concentration of
water at saturation. boundary layer). Note that adverse
microclimatic conditions may prevent
Of course, values of ct> are affected hy a reliable testing. Most E'IWironmental
the convective exchange with the circumstances require increasing the
ambient described by the term uRT d- 1• level of transpiration. During outdoor
This is usually difficult to be determined surveys, the weather can change
in real tests. In the laboratory, cf> was quickly, so the operator has to
directly obtained by weighing the tested measure temperature and relative
sample. In such a way, an evaluation of humidity periodically. The indoor
parameters affecting the evaporation microclimate may vary too hut in a
phenomenon in natural convection has longer time scale than that needed for
been ohtained?f~ the scanning. Hence relative humidity
and air temperature can be measured
Testing Procedure only at the beginning of the test, after
it and at any significant change of the
A preliminary scanning from a point as setting.
far from the masonry as possible makes it
possible to set the camera parameters and 3. Normally, the infrared camera is set at
to detect the anomalies in a few images, the maximum sensitivity. In fact, the
covering the whole surface. Further cooling effect of evaporation gives
measurements closer to the surface permit stnall differences of temperature. The
more precise analysis for small manual setting of the readout range is
discontinuities. preferable, even if some detail of the
infrared image can he out of scale.
The classification of the surface in Furthermore, the average function h
more or less homogeneous areas is usefully applied in case of noisy
achieved in almost steady thermal state images because of smooth temperature
because of natural boundary conditions, variations.
according to the following steps.
4. The choosing of the fidd of view
1. Collect the available description and depends on the lens and on the
plans of the building; the particular distance. Normally, a double scale
building technology; information taking is suggested.
about the masonry, finishing and all
material used; and the survey of the 5. The identification of the damp areas is
present state of damage due to achieved by comparing the
moisture. temperatures of the dry surfaces to
those of the moist surfaces. In the case
2. A suitable geometrical drawing of the of wide surface the investigation may
interior and exterior of the building at require the shooting of numerous
adequate scale represents the template thermograms, which will be composed
on ·which the visual state, into a composite image.
thermograms and others ancillary data
will be superimposed. Thermograms may be assembled into
composite images through the following
3. The actual boundary conditions and process.
particularly the temperature, relative
humidity and solar irradiation have 1. Some removable marks are placed on
been recorded for at least 24 h before the surface to identify the position of
the thermogram is recorded. the thermogram borders.

Boundary conditions arc controlled as 2.The operator has to record also the
follows. pattern of the shots during the
inspection.
1. The inspected surface has to be kept
out of direct heating for about 12 h 3. The position of the camera has to be
before the scanning, because different as perpendicular as possible to the
absorption coefficients of the surface surface.
cause effects contrasting the cooling
due to the evaporation. 4. For optimum matching, correction of
the perspectivt' distortion is needed.

S. lf a selected palette is permanently
associated to the thermogram by the
digital image format, it has to be
recorded also in grayscale. Additional
palettes can be used in the final
editing of the images.

640 Infrared and Thermal Testing

Effects of Moisture on Thermal (8) T 2 (l {L
Parameters
<' \ rr
Thermal properties mainly influenced by
where Q is absorbed energy (watt) and I is
moisture are heat capacity c and thermal time (second).

conductivity k. \Vater fills pores inside Assuming that effusivity of a moist
material making it heavier and more material is £'(H') = l1+w(c1Jc)]-0·\ the finJ:I
thermally inertial due to its high specific equation for determining moisture
heat (cw = 4181.1 }kg--l.K-1), compared
\Vith that of dry building materials content w was proposed in the following
(c.,= 800 + 900 ]-kg-l·K-1) and its
considerable density (p = 1000 kg·nr~). form:

lvfoisture w is specified on dry specimen (9)

base: The accuracy in moisture measurement
by Eq. 9 depends mostly on the ilccmacy
(4) w in determining absorbed energy. To loosen
this problem, a reference technique has
where Mw is masses of water and Md is dry been introduced.76 Adopting this
specimen. For physically dear rea~ons: approach, Eq. 10 gives the water content
value for the moistened material:
(5) M(w)

(6) c(w) M(w)

(7) C(W) = where '/~is the temperature from the
surface of the reference area.
The variation of thermal conductivity
with moisture is a much more complex Equation 10 assumes that conductivity
matter, not yet fully understood, and does not vary significantly with water
most of the proposed models are content. Finally, here the ratio of
semiempirical79 Considering that the absorptivity coefficients of the surface in
thermal conductivity of water, the appropriate spectral range (al\"2 u,fz) is
kw = 0.58 f\'\'·m-1·K-1], is much higher introduced.
than the conductivity of moist air in the
pores, ka = 0.026 IW·m-l.K-1], an increase If the impinging one-dimensional heat
of conductivity ·with water content is to flux is described by a harmonic function,
be expected. As a consequence, the effect as periodic natural sources, then the
of moisture on conductivity is an moisture influences the amplitude and
informative parameter. Because heat can shape of surface temperature response.
be transported both by conduction and Then, the temperature patterns can he
water flow, however, the exploitation of inverted <IS well applying an iterative,
the thermal conductivity to detect moist nonlinear least squares technique59
zones is quite ambiguous.
Testing Procedure (Active and
The dependence of thermal inertia or Relative)
effusivity (e = \1(kc) versus moisture is
straightforward and makes this parameter An active approach is used in this case but
attractive for the moisture monitoring. in some cases solar radiation is sufficient.
Building parts of larger thickness could be Artificial heat sources are normally limited
considered as semiinfinite bodies and heat to a selected area.
flux one-dimensional. As a result, the
corresponding mathematical solutions The succeeding steps are to be
substituted to the previous procedure for
become simpler than those for a slab. the surface classification:

Such a solution a1Iows solving the inverse 1. Apply a suitable heating, about
problem in an explicit form. On the other I kW·nr2 (-320 BTUrch-1·ft-2 )
hand, this approach requires an active starting just after the first thermogram
stimulation of the surface, reducing the has been taken,
tested areas if an artificial source is used.
In the adiabatic case, the surface 2. Record a sequence of thermograms for
temperature is given in a very simple at least 15 min using if possible a
form, after a step heating: logarithmic time scale (if not possible
use a constant grabbing frequency
according to the capJ:bilities of tlw
system).

:1. Process the data using Eq. 10.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 641

Examples of Detection of Damp the eastern side (air temperature
Areas by Evaporative Flux 296 K = 23 oc = 73 oF, relative humidity
67 percent). Gtavimetric tests confirmed
The thermal hygrometrical status of the the presence of water. The water content
masonry of the Oratorio della Guardia di resulted 11.6 percent on bricks at 0.50 m
Satta, Corsica, Italy, was measured from 20 in.) from the ground; 7.2 percent on
1995 to 1997 (see Fig. 37a). brick at 0.98 m (39 in.) in area 1 and
Thermographic monitoring '''as 3. 6 percent in area 2.
performed to study the dependence on
climactic changes. Periodically, The infrared images of Fig. 39 have
gravimetric tests verified the water been taken at Sant' Massimo Church,
content and thermographic results. Sedriano, Italy. It shows the distribution
Gravimetry measures quantitative water of rising damp at the base of the facade
content as a percentage of weight. The wall. Here, the damp areas appear warmer
building has structural masonry and lime during the night, after 12 h of solar
mortar. In Fig. 37b is shown an infrared irradiation (15 May 2000, air temperature
image (21 November 1995, air
temperature 280 K = 7 oc = 45 °F, relative 290 K = 17 oc = 63 oF, 85 percent relative
humidity 57 percent, clear sky). Smooth
gradients found on thermal images humidity).
indicate a rather homogeneous moisture Thermograms recorded on 21 March
distribution although gravimetric results
verified a high water content. The high 1995 show the visual state of the western
humidity percent and low air temperature side of Santa lv1argherita church without
mitigate against a sharp separation of wet active heating of the surface. The base of
from dry areas. In fact, under these the masonry appears colder and wet.
conditions evaporation is at the Gravimetric tests confirmed the higher
minimum. On the contrary, passive 'i\'ater content in that zone of the wall.
thermography detected rising damp on
16June 1997. The picture of Hg. 40a shows Sant'
Abbondio Cloister and the thermograms
Figure 37c shows the thermograms of of Hgs. 40h and 40c indicate the rising
the facade. A colder area is evident in the damp affecting the base of the wall. The
lower part of the facade. Notice that the damp area expands near the corner with
growing vegetation partially covers the the north side {right side) following the
left side of the door (area 2). 1n addition, shape of the decay of the p(trget.
Fig. 38 shows the infrared image shot on Thermograms ·were acquired by using the
passive technique. In this case, the high
correlation between the visual and
temperature pattern corresponds to an

FIGURE 37. Facade of Oratory of Gu.ard!a di Sotto, Corsica, Italy: (a) visible light photog~aph; 0(b) therm~gram o~ f.ar;ade does
any moisture accumulation (21 November 1995, a1r ~emperature 28
not reveal 0 K := 7 C =:, 45 F, r;lat1ve ~urn1d1tX .

57 percent, clear sky); (c) passive thermogram (16 june 1997, a1r temperature 296 K ~ 23 C ~ 73 F, relattve humtdtty

67 percent).

(a) (b) (c)

legend

1. Colder, moister areas in lower part of fa~ade.
2. Vegetation partially covering left side of door.

actual moisture distribution as confirmed FIGURE 40. Sant'Abbondio cloister, Cremona,
by gravimetric measurements (20 june Italy, 20 June 1995: (a) visible light
1999, air temperature 298 K ~ 25 'C ~ 77 photograph; (b and c) passive thermograms
0 1~ relative humidity 40 percent). showing rising damp in" masonry. Air
temperature 298 K (25 'C ~ 77 'F), relative
In the case of Corte Castiglioni Manor, humidity 65 percent.
Mantova, Italy, the building is made of
structural masonry, bricks and lime (a)
mortar.!:!° Chemical physical analyses
varied greatly because of the different
kinds of mortars and bricks used.
Furthermore, their absorption coefficients
vary in a few centimeter square (a kw
square inches) of the surface.
Nevertheless, Fig. 41 acquired according

FIGURE 38. Passive thermography indicates
rising damp on lower part of masonry in
oratory of Guardia di Sotto, Corsica, Italy,
16 June 1997. Airtemperature 296 K
(23 'C ~ 73 'f), relative humidity
67 percent.

(b)

legend

1. Colder, moister areas in lower part of fa~ade.
2. Warmer and drier masonry.

FIGURE 39. Image composed of infrared thermograms shows (c)
distribution of rising damp at base of facade of San Massimo

Church, Sedriano, Italy, 15 May 2000. Damp areas appear

warmer at night, after 12 h of solar irradiation. Air
temperature 290 K (17 'C ~ 63 'f), 85 percent relative
humidity.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 643

to a passive procedure clearly indicates thermography in Fig. 43b allow~ locating
rising damp as colder areas 1 and 2 at the the distribution of damp an•as. Causes
base of the wall (17 june 1998, air have been identified both in rising damp
temperature 298 K = 25 "C::::: 77 "F, relative from the pavement and the local leakage
humidity 74 percent). The three strips of a pipe (17 June 1999, air temperature
detectable by thermography correspond to 299 K::: 2() "C::: 79 "g relative ·humidity
the average water content decreasing with 54.3 percent).

height. limitations of Infrared
In Santa Maria in Cantuello (21 :1\•farch Thermography

1997), thermography was used to locate Constraints on Field Applications
damp areas. The thermogram was
recorded using the passive technique on After a period of laboratory
one side of the building. ~vfoisture ·was due experimentation and theoretical
to the leakage of an external basin. modeling, the application of infrared
thermography has been optimized in the
The visual state of the sacristy of Santa field. The effectiveness of tile analyzed
Maria del Lavello is shown in Fig. 42a, techniques and influences of some
where the state of decay of the plaster is conditions in real tests are discussed
evident. The actual extension of the damp below.
area is shown in the thermogram of
Fig. 42b. Notice that the moist surface (at FIGURE 42. Santa Maria del Lavello1 Bergamo,
the right side of the basin) is more Italy, 19 March 1998: (a) visible light
extended than the ruined one (19 March photograph of sacristy; (b) demarcated
1998, air temperature 287 K = 14 "C =57 damp area larger than damaged parget
"l~ relative humidity 38.8 percen.t). zone in sacristy. Air temperature 287 K (14
oc = 57 oF), relative humidity 38.8 percent.
In Addolorata Church, Gessate, Italy
(20 March 1996), the visual state of the (a)
interior plaster did not show any mark of
decay but infrared thermography revealed
the extent of recent leakage from the roof
on one side of the vault.

During the renovation of the plaster at
lstituto Musicale Donizetti1 Bergamo,
Italy, two sets of tests were performed to
localize the cause of infiltration. In
Fig. 43a it is shown the state of decay of
the plaster in a key zone near the down
pipe. The diffused damage prevents
identification of any indication of direct
infiltration. Nevertheless, infrared

FIGURE 41. Thermography of facade of Corte
Castiglioni, Mantova, Italy, 17 June 1998.
Three bands correspond to water content
decreasing with height. Air temperature
298 K (25 oc = 77 oF), relative humidity

74 percent.

(b)

legend
A. Relatively dry.
B. Moderately cool and damp.
C. Cold and damp.

644 Infrared and Thermal Testing

In situ applications require the temperature change. On the contrary, the
procedure to be as fast as possible, to keep passive approach works at steady state.
constant the condition of the scanning
and to reduce the costs. Passive SURFACE CoNDITION. Oftt>n hhtorical
techniques have the advantage of being buildings lt~ck homogeneous surfaces,
much more productive and easily applied either in color or material. Difference~ of
to surfaces larger than 10m2 (108 ft2). On heating absorption affect the thermal
the contrary, using artificiJl sources only a ;malysis, causing false alarms and altering
small area can be homogeneously heated. the thermal response of the structure.
Moreover, effective radiating requires a Ptlfticult~rl)' in the case of frescoes and
powerful power supply (more than :1 k\IV). paintings the artificial heating (for
The sources must be supported close to instance by lighting) increases such a
the surface with expensive scaffolds. As a difference. Furthermore, salt deposits
consequence, it is necessary to scan the modify reflectance and emissivity. Soluble
whole surface in smaller areas of 1 to 2 m 2 salts arc ever present in a surface d(lmag(•d
(1 0 to 22 ft2). Additional time is needed by damp. (Jenerally, deposit of salts
for the transient analysis. In fact, a decreases the emissivity, causing an
sequence of thermograms is recorded and apparent temperature lower than true.
each pixel processed in its turn. The only
advantage of the active procedure is the THERMOGRAPHY SETIING. Usually
reduced dependence on environmental thermography is applied in the
conditions. Hence, the active approach preliminary phase, to obtain the
can be applied also in case of presence of information necessary to plan the
other (not removable) sources of heating, intervention. In this phase the yard of
because the estimation is based on conservation is not settled yet, so the cost
of the scaffolding could inflate the cost of
FIGURE 43. lstituto Musicale Donizetti the project. Also in the maintenance
Bergamo, Italy, 17 june 1999: (a) visible program, where thermography is applied
light photograph of plaster of northern side; as ·well, the cost of the scaffolding or
(b) thermogram of plaster indicating cooler, pickup elevator could make active
damp area (darker zone) due to pipe thermography inconvenient. Qualitative
leakage. Air temperature 299 K (26 'C = analysis may help in such a situation.
79 'F), relative humidity 54.3 percent.
(a) HEATING. Artificial heating must be applied
as perpendicularly to the smface and as
(b) diffusely as possible. In cases of heating
from long distances or from the bottom of
elevations, artificial heating could be very
uneven. An autonomous power supply
could be ne<.:essary. In many cases the
temperature increase must be limited to
only a few degrees, because of the
preciousness of the surfaces.

The healing of aU the layers of thl'
structure is hardly achievable: the low
thermal diffusivity and the wideness of a
building requires long and powerful
heating. The direction of the heat flux
should be one-directional but the
discontinuities of the surface modify the
propagation of the heat inside the
structures.

VISUAL ANALYSIS. The Visible damage of the
materials docs not correspond to the
actual state of the masonry. For example
cracks in the co(lting, in the plasters and
in the external layers sometimes can be
smaller than inside damage and traces of
damp. Stains, salt deposits, increases of
porosity, delaminating of plasters, voi{h
and other kinds of damage may occur
even if water has dried. Furthermore, the
damage of the surface often modifies
locally the imposed heat flux,
complicating the diagnmh. Neverthek~~,
the availability of the picture of the
surf<Ke is extremely useful.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 645

Integration with Other Testing
Techniques

Thermography allows moisture
distribution in the surface to be mapped.
The results are qualitative only and are
restricted to the surface. There is no easy
correlation between the temperature
measured and the '"later content.

The integration with other quantitative
techniques (for example, gravimetric
testing) is suggested. A moisture map
obtained nondestructively by
thermography makes it possible to
decrease the number of samples to collect
without affecting the reliability of the

tests.Hl

A variant of the active heating involves
microwave radiation.82 In this case, the
water selectively absorbs the energy. The
drawback of this technique is· the more
complex managing of the heat source.

The measures could be repeated on the
same wall in different periods of the year.
Further validation by gravimetry also
permits the paths of the water coming
into the wall from the sources to be surely
determined.

The tradeoff beh\'een a complete
refurbishment and a detailed but
circumscribed diagnosis push toward the
latter- particularly for historical
buildings where the cultural heritage must
be preserved.

646 Infrared and Thermal Testing

PART 6. Infrared and Thermal Testing for
Conservation of Fine Art83

The scientific examination of art can he 1. For inspection of the surface,
divided into two basic categories: conservators use ultraviolet fluorescent
destructive and nondestructive. Among photography. Ultraviolet light will
the destructive methods are those that cause old varnish to fluoresce.
involve sampling, taking a small slice or Therefore, if portions of the protective
scraping for closer scrutiny, perhaps by varnish do not fluoresce under
microscopy or thermoluminescence. A ultraviolet light or if they appear
conservator's goal, however, is to carefully darker than the surrounding area, it
maintain valuable works of art and to can be assumed that relatively recent
slow the inevitable deterioration. changes have been ma.de to the
Nondestructive testing is an invaluable surface. Unfortunately, as the newer
tool to this end. The art historian also varnish begins to age, it too will begin
finds nondestructive testing an important to fluoresce and then the conservator
asset in the pursuit of information of has to use another method to look
historical value - for example, about under the surface.
creative techniques of a particular artist or
a certain period of art. 2. x.radiography records the distribution
of pigments that have a high
Three-Dimensional Art absorption coefficient for X-rays. The
X-rays used in X·radiography will
Three-dimensional art includes completely penetrate a canvas.
architecture and sculpture and infrared However, if pigments such as white
thermography finds applications in these lead or vermillion with high
fields. Nondestructive testing methods absorption coefficients are present,tiH
applied in building maintenance and their distribution will be indicated on
restoration is in many cases the same as a photographic plate placed behind
that used for art conservation. Such the canvas.
applications of thermography are
represented in the literature.s6,H4·87 3. A third part of the electromagnetic
Conservation of frescoes, paint on plaster, spectrum used in the nondestructive
is a special case of interest to both testing of art is infrared.
building and art conservationists.H77
Nondestructive testing technologies also Infrared Techniques
find applications in archaeology and
anthropology. The balance of the present Infrared waves will penetrate different
discussion focuses on painting on canvas. pigments with varying effectiveness. The
degree of transparency depends chiefly on
Two-Dimensional Art wavelength (the longer the wave, the
greater the degree of transparency),
As part of the creative evolution of a thickness of the paint film and reflection
painting, an artist will often change his or or absorption properties of the pigment.~'W
her mind during composition and paint Carbon black is the most absorptive;
over the original idea. The artist may even white is the most reflective. Infrared film,
paint over one of his earlier works if the used in infrared photography, is receptive
artist considers the painting less only to the portion of the spectrum with
important than the need for another wavelengths up to about 900 nm. At
canvas. A change can also be made by those wavelengths, not all colors will
someone other than the original artist. allow infrared penetration with the same
From the art historian's point of view, facility. Green and blue, for instance, have
these underpaintings can afford insight absorptive qualities very similar to those
into artistic development or the of black and may !Je opaque whereas
techniques used to achieve a particular brown and red generally reflect about the
effect. They can also help determine the same as white.YO
artist or the authenticity of a painting.
The typical arrangement for infrared
Three of the methods often used in the examination has a source of visible and
inspection of two·dimensional art use infrared radiation, an object to he
electromagnetic energy. Each of the three examined and an infran.·d recording
wave types is used to survey a different device or camera with an infrared filler to
layer of a painting. exclude all but the infrared waves.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 647

Photographic studio lights are used in a painting. This has been and still is the
darkened room. The lights are controlled most widely used procedure for
by a rheostat that dims them to the maintaining a permanent record.
infrared range.91 The radiation produced
at this point is very largely infrared with Renaissance Netherlandish
little of the visible portion of the light Art
spectrum. This source is aimed at the
painting. \'\1!1en infrared waves reach the Flemish artists of the fifteenth and
painting, they will penetrate the surface sixteenth centuries were very consistent
and the recording device takes the in their mettwd of producing paintings.
ensuing picture. Years of grime or cloudy, First, the artist covered an oak panel with
darkened varnish are not obstacles: they a ·white preparatory surface, or ground,
are easily penetrated by infrared radiation. that was a mixture of chalk and animal
Contrasting reflected waves are collected glue. The next step was the preliminary
by the infrared camera to produce a sketch made with carbon black or charred
record of the paint layers beneath the bone mixed with water. These two
surface. elements make this period of art
amenable to inspection with the infrared
Infrared pJ1otography using a 35 mm reflectographic technique. The white
ground ensures that the infrared rays not
camera and infrared film has been used absorbed by the black portions of the
since the late 1950s at conservation sketch are reflected back to the camera.
laboratories. One such laboratory is the The carbon black sketch produces a very
Intcrmuseum Conservation Association, visible contrast against the white ground.
Oberlin, Ohio. This facility was
Although best results are obtained with
established in 1952 as a cooperative Netherlandish panel paintings, French,
conservation lab. Some of the typical German and Italian art from the same
examination procedures used in the period will sometimes give good re!iults
Oberlin lab are illustrated by the infrared although certainly not with the same
photographs of Charles Baum's Bo}' with frequency as the Flemish art.
Still Life, owned by the llutler Institute of
American Art and once attributed to The Paintings Conservation
another artist, Severin Roesen. Figure 44a Department. of the Metropolitan J\Juseum
shows a photograph of the portrait using of Art, New York, in a project conducted
normal, visible light. No images other by 1vfaryan Ainsworth, examined the
than that of the title are apparent. An 1:aintings of joos van Cleve, an early
infrared photograph of the same painting SIXteenth century Delgian artist. None of
shows a sketch, or underdrawing, of the his drawings on paper were thought to be
face of the young boy and the faint image still in existence. Because the
of a young woman slightly above and to underdrawings of his paintings were so
the right (Fig. 44b). X-radiography (Fig. much easier to discern using
44c) reveals a third image and appears to reflectography, van Cleve's graphic
be that of an older man. In addition vocabulary became apparent. \•Vith this
new acquisition, Ainsworth was able to
darker areas slightly below center and attribute to van Cleve previously
unidentified drawings on paper.
lower left indicate some restoration.
The newest addition to infrared An interesting note in infrared
investigation of this period is that it
examination is infrared reflectography, afforded insight into ·workshop
developed by ].H.]. ~'an Asperen de Boer techniques of reproduction. If a painting
specifically for fifteenth and sixteenth exhibits underdrawings or changes in
century Netherlandish panel paintings. composition, it is probably a prototype
This system uses a vidicon camera to and attributable to a single artist.
capture the infrared image and transmit it However1 artists often copied their most
to a black-and-'white monitor. The vidicon popula~ paintings. The work of copying
tube is receptive to the entire infrared these pieces was delegated to other artists.
spectrum and the blues and greens One copying technique, called pouncius,
become transparent to the-longer uses a line drawing on paper pierced
wavelengths. An excluding filter, opaque along the outlines. This paper pattern was
to wavelengths belmv about 0.9 pm, placed over a canvas and black carbon
admits infrared \Vaves up to 2 pm. powder was rubbed through the holes to
produce a matching image on the canvas
Reflectograms are the photographic beneath. This image was then painted in
record of infrared refJectography. to match the original. Visible in
Typically, to obtain a detailed overall reflectography, these tiny dots of carlJOil
image of a painting, the vidicon camera is indicate a copy and therefore worksllOp
aimed at part of the canvas and the irnage production.
displayed on the monitor is
photographed. This process is repeated
until the entire canvas has been captured
on film. These discrete photographs are
then carefully arranged in their correct
sequence to produce a whole image of the

648 Infrared and Thermal Testing

Vermeer defined images of undersketches. Though
his paintings do not contain the defined
Arthur K. Wheelock, Jr., in research as a
National Endowment for the Arts Fellow, underdrawing used in earlier centuries,
used reflectography as a n1ethod reflectography has revealed roughly
complementary to X-radiography in blocked-in forms. View of IJelft, known for
relating the painting techniques of the realistic impression it gives, was
seventeenth century Flemish artist jan examined by \o\'heelock. The painting is a
Vermeer to his distinctive style.92 Because cityscape of the seventeenth century
Vermeer used carbon black to do his mirrored in the still waters of a harbor.
sketching, reflectography can provide well Using infrared and X-radiography,
\-\'heelock was able to determine the

FIGURE 44. Charles Baum's Boy with Stiff Life, previously attributed to Severin Roesen: (a) visible
light photograph; (b) infrared photograph shows underdrawing sketch of boy's face and
image of young woman; (c) X·radiograph of entire canvas shows image apparently of older
man.

(a) (b)

(c)

Infrastructure and Conservation Applications of Infrared and Thermal Testing 649

changes made in the length and especially when they appear to be done
positioning of the reflections in the water by someone other than the original
cmd in the outlining of the city's profile: mtist?2
changes that Vermeer made to achieve his
realistic effect. Randall's Mill

ln addition to learning more about The painting RnndnW< Mill ( 1922-23) by
Vermeer's working techniques, \·Vheelock American artist Victor Higgens was
attempted to determine compositional examined by the Intermuseum
changes and also to learn more of actual Conservation Association laboratory
physical condition - that is, abrasion, (Hg. 4Sa).9.1 The painting was presented to
restorations or any sort of alteration of the Snite Museum in 1982 by William
size. Some changes to a painting can
result in questions of authenticity,

FIGURE 45. Victor Higgens' Randall's Mill: (a) visible light photograph; (b) infrared reflectogram shows complex of mill buildings
and figures in foreground, including human and donkey; (c) X-radiograph shows mill of title.

(a) (b)

(c)

.....,., ;.;: .-).

650 Infrared and Thermal Testing

Harmsen and wife of Denver, Colorado, penetration depth of the exciting
stiH on the original canvas stretcher and radiation and (3) the sensitivity of sensors
in a frame with a brass label that reads: used in the design of the available system.
"VICTOR HIGGENS NA [sic] I 1884-1949 I A technique called raman spectroscopy has
RANDALL'S MILL." shown promise for in situ examination of
fine art and archaeological artifacts_94,95
Porter noticed that, in light from an
adjacent window, the raised surface of An image spectroscopy system has
another painting appeared on the canvas. been proposed and shown to be capable
After examining Randall's Mill under a of collecting sequences of images at
raking light, the Oberlin laboratory several wavelengths. Suitable procedures
assayed the oil*on*canvas painting with were developed for calibrating and
various methods including X~radiography spatia11y registering the acquired data. An
and infrared reflectography. The painting experiment on a test panel painted with
appears as a depopulated landscape, but, known pigments showed that image
when the painting is viewed by infrared processing is a powerful tool for pigment
reflectography, the structure of a mill identification when used with spot
appears along with carriages filled wHh spectral analysis. Measurements in one
figures, horsedrawn wagons and the figure case reveal that the methodology is valid
of a saddled donkey being led by a man and can give additional information that
(Fig. 4Sb). Photographic images of the is otherwise not easily extracted.96
infrared reflectography examination were
made from the black and white monitor A sixteenth century drawing attributed
as the camera scanned various portions of to the school of Pieter Bruegel the Elder
the canvas. With X-radiography, the had been damaged by cleaning. Near
structure of the mill is the dominant infrared spectroscopic imaging was used
element (Fig. 4Sc). to analyze the remnants. Using a
combination of a charge coupled device
A }Jainting of this description by camera and a liquid crystal tunable filter,
Higgens was detailed in the Indianapolis near infrared spectroscopic images (650 to
Star in 1924 but the painting 1050 nm) ·were collected from the
subsequently disappeared. In an interview drawing and from a test sample composed
in 1975, Helen Spiess Ferris, daughter of of four substances with various near time
Benjaman G. Randall, a civil engineer resolved spectra deposited on a white
who had settled in Taos, New Mexico, board. Linear discriminant analysis and
related the tale explaining the painting fuzzy C-means clustering were used to
beneath a painting. Randall had built t11e analyze the data. Fuzzy C*means
mill of the title. In the vicinity of the dustering with spectral normalization
mill, he owned a cabin that he made routines proved an excellent data
available to the artist Higgens. Higgens exploration technique for the test sample.
painted the picture of Randall's Mill from Linear discriminant analysis gave
that cabin. Upon seeing the picture, consistently clearer results than the fuzzy
Randall pronounced it 11the worst picture C-means technique but required prior
Higgens ever painted." The statement knowledge of the spectral properties of
must have bothered Higgens for some the sample; fuzzy C-means analysis
time, for the overpainting is in a style provides such spectral information. Linear
that Higgens used much later during the discriminant analysis of the spectroscopic
1940s. image located faint traces of ink residue
on the drawing??
Spectroscopy
The most widely established
Spectroscopic techniques involve analysis spectroscopic methods are not thermal.
of the spectrum of radiation emitted from For analysis of metal objects, X-ray
a test object in order to identify the fluorescence (XRF) spectrometry uses low
chemistry of the radiating material. energy X-rays or gamma rays to excite
Spectroscopy can be destructive in cases characteristic X~rays in the suhject
where the design of the inspection material. Sensitive laboratory X-ray
hardware requires removing a sample of fluorescence systems exist with advanced
material from the art object. However, detectors and microelectronics, coupled
some nondestructive spectroscopic with advanced computer technology.
designs permit the identification of Portable units can yield precise readings
materials in situ and these are likely to be in the laboratory and in the field?~>
more valuable for those who study or
conserve works of art. Spectroscopy is Other Thermographic
performed at wavelengths in X-ray, Applications
ultraviolet, visible and infrared
frequencies. The wavelength used for the William A. Real, while a }vfellon Fellow at
test is a function of test patameters such the Cleveland :ivfuseum of Art, Cleveland,
as (1) the material of interest, (2) the Ohio, explorPd the broad potential of

Infrastructure and Conservation Applications of Infrared and Thermal Testing 651

ii-1frared reflectography as a research tool.
He inspected successfully not only
paintings but objects, manuscripts and
graphic works on paper. In addition to
fifteenth and sixteenth century Northern
European ait, Heal has examined works as
diverse in media and period as paintings
by I~rench artist j.A.D. Ingres of the late
eighteenth and early nineteenth century;
a portable carved, wooden japanese shrine
attributed to the Heian period (795-1185);
a surrealist collage by Max Ernst, jeanne
Hachette et Charles le Tememire (1929), on
paper; and an East Indian min'1ature
Pradywnna, Son of Krishna, mzd His Wife
Maya Fl}•ing through the Air (ca. 1750),
color on paper. Real has discovered
preparatory sketches under layers of
grime, stain and coatings on the japanese
shrine, indicating it is unfinished. He has
discovered compositional changes and
even hidden inscriptions in the East
Indian piece and improvisational changes
(painting over already dry paint) as well
as underdrawings in Ingres' Antioclws and

Stratonice.

The infrared method has continued to
be developed. The Jvlctropolitan Museum
of Art in conjunction with the
manufacturers of sofh\•are programming
have investigated a system to digitize the
reflectograms (images from a vidicon
camera) and join them in one complete1
permanent electronic record. The
portability of the system (examination
and recording) is such that it can be rolled
right into the galleries where the
paintings can be examined and a
permanent record of the results can be
obtained.

Information pertaining to technical
inspection of art has not always been
extensively published and therefore has
not been widely applied. Hmvever,
because of growing awareness by
museums and private collectors, the
advances in nondestructive test methods
and infrared inspection in particular have
found ·wide acceptance and application in
art conservation.

652 Infrared and Thermal Tesfmg

References

I. Wei!, G.]. and T.G. McRae. Chapter 12, 9. -Jnagaki, 1: and Y. Okamoto. Diagnosis
of the Leakage Point on a Structure
"Infrared Thermographic Leak
Testing.11 Nondestructive Testins Surface Using Infrared Thermography
Handbook, third edition: Vol. 1, Leak in Near Ambient Condition." NDT&E
Testing. Columbus, OH: American Iutemational. Vol. 30, No. 3.
Society for Nondestructive Testing Amsterdam, Netherlands: Elsevier
(1998): p 505-520. Science (March 1997): p 135-142.

2. Chapter 6, "Thermal and Infrared 10. Okamoto, Y., T. fnagaki and T. Suzuki.
Nondestructive Testing." Nondeslntctive Use of Radiometer to Reform and
Testing Handbook, second edition:
Vol. 9, Special Nondestructive Testing Repair an Old Living House to Passive
Methods. Columbus, OH: American Solar One.11 Tllemwsense [Orlando, J:L,
April 1994]. SPJE Proceedings,
Society for Nondestructive Testing Vol. 2245. Bellingham, WA:
(1995): p 307-362.
3. Botsko. R.[J.] and T.S. jones. International Society for Optical
Chapter 13, "Thermography and Engineering (1994): p 64-51.
Other Special Methods." Nondestructiw
Testing Handbook, second edition: Vol. 11. Inagaki, T., K. Suzuki andY. Okamoto.
10, Nondestructive Testing Ovetview. Study on Visualization Techniques of

Columbus, OH: American Society for Temperature Distribution in Air How
Nondestructive Testing (1996): by ?v1eans of Infrared \'\'ire-Net."
p 478-502. Proceedings ofthe 4t!J Triemmial
International Symposium 011 Fluid
4. Wei!, G.]. "Infrared Thermography Coutrol, Measurement and Visualization
- FluCome [Toulouse, France, August
Based Pipeline Leak Detection 1994]. Toulouse, France: Office

Systems.11 Thermosense 13. Vol. 1467. National d'Etudes et de Recherches
Bellingham, WA: International Society Aerospatiales (1994): p 321-326.
for Optical Engineering (1991 ): p 18. 12. Cadoni, E. 11 Experimental Study on

5. Ljungberg, s.A. "Infrared Techniques Concrete Fatigue by Means of Pull-Out
Test." Fatigue '96: Proceedings l'llh
in Buildings and Structures: Operation lntemational Fatigue Congress. Vol. 3.
and Maintenance.11 Infrared Berlin, Germany: Pergamon (1996):
A1etlwdology and Technology. p 1621-1626.
Langhorne, PA: Gordon and Breach
Science Publishers (1994): p 211-252. 13. Stroeven, P. "lvfechanisms of Damage

6. Lunungberg, S.-A. "State-of-Art and Evolution in Lmv-Cycle Compression
Future Plans for IR Imaging of Gaseous r:atigue of Concrete." Fatigue 96:
l:ugitive Emission." Thermuset1se XIX. Profeedings of t!Je 6th Inlt'matioual
Orlando, SPIE Proceedings, Vol. 2774. Fatigtte Congress [Berlin, GennanyJ.
Vol. 3. Oxford, United Kingdom:
Bellingham, WA: International Society Elsevier Science, Pergamon Press
for Optical Engineering (April 1997):
(1996): p 1615-1620.
p 2-19. 14. VaJluvan, R., M.E. Kreger and J.O.
7. \Veil, G.]. "Nondestructive Remote
Jirsa. "Strengthening of Column
Sensing of Hazardous Waste Sites." Splices in Infilled Shear Walls."
ASNT Fall Conference and Qua/it)' Earthquake Engineering: 1Oth JVorld
Testing Show [Dallas, TX]. Columbus, Conference. Vol. 9. Rotterdam,
OH: American Society for Netherlands: Balkema (1992):
p 5121-5126.
Nondestructive Testing (October
1995): p 137-139. 1S. Carpinteri, A. "Fatigue Crack Growth
in Reinforced Concrete."
8. Ishibashi, A., H. Miki and 'J: Fujiwara. Micromechanics ofPailure of
"Application of Thermal infrared Quasi-Brittle Materials. London, United
Kingdom: Elsevier Applied Science
Remote-Sensing to Shotcreted Slopes.'' (1990): p 541-548.
Tile First US-Japan Symposium 011
Ad1•ances in NDT fKahuku, HI}.
Columbus, OH: American Society for

Nondestructive Testing Oune 1996):
p 414-419.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 653

16. Nakashima, S. "Mechanical 26. Robinson, <i.S. "Behavior of Concrete
Characteristics of Steel Column-Base in Biaxial Compression." Journal of
Connections Repaired by Concrete Structural Dil'isiou. VoL 93. Paris,
Encasement." Earthquake Ensineeri11s: France: Association Fran\'aise du Genic
10tlll-\Turld Conference. Vol. 9. Parasismique (1967): p 71~86.
Rotterdam, Netherlands: Balkema
(1992): p 5131-5136. 27. Vile, G.W.D. "The Strength of
Concrete under Short~Term Static
17. Izuno, K. and T. Ohkawa. Biaxial Stress." Jntemational Omfi-'rence
Structure of Concrete. \r\'exham Springs,
"Quantification of Repair Effect for RC United Kingdom: Concrete
Association, formerly Cement and
Members Using Inelastic Earthquake Concrete A~sociation (1968):
Response Analysis." Earthquake p 131-145.
Engi11eering: 1Otll l-\Torld Conference.
Vol. 9. Rotterdam, Netherlands: 28. Luong, M.P. "Nondestructive Annlysis

Halkema (1992): p 5221-5226. of 1vficrocracking in Concrete."
18. Cornelissen, H.A.VV. "Fatigue Failure of lntematimwl Conference 011
NondestrucUw Testi11g of Conade in tile
Concrete in Tension." Heron. Vol. 29, lnfmstrudurc !Dearborn, ivHchigan).
No. 4. Delft, Netherlands: TNO Bethel, CT: Society for Experimental
Mechanics (1993): p 199-217.
Building and Construction Research
29. Ouyang, C., E. L;;mdis and S.P. Shah.
and School for Advanced Studies in
Construction (1984). "Damage Assessment in Concrete
using Quantitative Acoustic Emission."
19. Zhang, B.S., Z.H. Zhu and K.R. Wu. journal of E11gineering Meclumics.
"Fatigue Rupture of Plain Concrete Vol. 117, No. 11. Reston, VA:

Analysed by Fracture Mechanics." American Society of Civil Engineers
Fracture of Concrete and Rock: (1991): p 2681-2698.
SEM/RILEM h1ternational Cm1fi-'rei1Ce 30. Luong, M.P. "Infrared Observation of
(Houston, Texas, june 1987J. New
York, NY: Springer-Verlag (1987): Failure Processes in Plain Concrete."
p 58-63. Durability of Btlildillg Materials and
Components: 4DBMC !Singapore,
20. Papa, E. A11 Damage lvfodel for Republic of Singapore, November
Concrete Subjected to Fatigue 1987]. Vol. 2. Oxford, United
Loading." European Journal of
Mechanics- A/Solids. Vol. 12, No.3. Kingdom: Elsevier Science, Pergamon
Paris, France: Elsevier Science, Press (1987): p 870-878.
Gauthier-Villars (1993): p 429-440.
31. Luong, M.P. "Infrared Thermographic
21. Suresh, S. "Fatigue Crack Growth in Observations of Rock Failure."
Cementitious Solids under Cyclic Comprehensive Rock Ensi11eerius
Principles, Practice and Projects. Vol. 4.
Compression: Theory and Oxford, United Kingdom: Elsevier
Experiments." FractiiH' u( Concrete mul Science, Pergamon Press (1993): p
Rock. London, United Kingdom:
Elsevier Applied Science (1989): 715-730.
p 162-172. 32. Luong, M.I~ "Infrared Thermographic
22. Zhang, B.S. and D.V. Phillips. ''Fatigue
Scanning of Fatigue in Metals." Nuclear
Life of Plain Concrete under Stress Eugineerins mul Design. Vol. 158.
Reversal." Fracture of Concrete and Rock. Amsterdam, Netherlands: Elsevier
London, United Kingdom: Elsevier
Science (1995): p 363-376.
Applied Science (1989): p 183-192. 33. Luong, ~vLP. "Geotechnical Fuse Using
23. Alliche, A. and D. Fram;ois. 1'Fatigue
a Soil~I;ibre Composite." Tnmsactions
Damage of Concrete." Fracture of' lSll1 ltltenwtimwl Cm1{etn1ce 011

Concrete and Rock; SElvf/RILElvf Stmctuml Metlwuirs in Reac-tor
llttenwtimwl C011(ere11Cl' (Houston,
Texas, june 1987]. New York, NY: TI:clmology (SMiRT-15). Vol. 8, Div. K:
Springer-Verlag (1987): p 88-95. Seismic Response Analysis and Design
-Part 1, K03/4. Seoul, Korea: Seoul
24. Luong, M.P. "Infrared Thermography
of Fatigue neht~vior of Concrete under National University, Korea Earthquake
Compression. 11 2nd Intemational
ConfereHce 011 Nrmdestmctiw Testius o( Engineering Research Center, for
Concrete i11 the lnfrmtmcture !Nashville, International Association for Structural
TennessseeJ. Bethel, CT: Society for
Experimental Mechanics (1996): Mechanics in Reactor Technology
p 167-176. (IASMiRT) (August 1999): p 121-128.
:14. Luong, i'v1.P. "Infrared Thermovision of
25. Zhang, B.S., D.V. Phillips and K.R. \·Vu.
Damage Processes in Concrete and
"Further Research on Fatigue Rock." E11giuceril(~ Frtlcllm• 'l\Jcclwllics.
Properties of Plain Concrete." Vol. 35, No. 1~2-3. Oxford, United
Magazine of Concrete Researcll. Vol. 49, Kingdom: Elsevier Science t}990):
No. 180. London, United Kingdom:
Thomas Telford Limited (September p 127-135.

1997): p 241-252.

654 Infrared and Thermal Testing

35. Luong, M.P. 11 Fatigue Limit Evaluation 46. CGSB 149-GP-lOM, Standard for
Determi1rali011 ofAittightness of'
of Metals Using an Infrared Buildings by tile Fan Depressurization
Thermographic Technique." lvleclwnics Method. Ottawa/ Canada: Canadian
of Materials. No. 28. Amsterdam, General Standards Board.

Netherlands: Elsevier Science (1998): CAN/CGSll-149.10-M, Determination of'
p 155-163. the Airtightness ofBuilding Envelopes by
the Fan Depressurization Method.
36. Sparks, P.R. and J.B. Menzies. "The
Ottawa, Canada: Canadian General
Effect of Rate of Loading upon the Standards Hoard (1986).
Static and Fatigue Strengths of Plain
Concrete in Compression." Masazim: 47. ASTM E 1186-87, Standard Practices for
ofConcrelt' Research. Vol. 25, No. 83. Air Leakage Site Detection in Building
Enl'elopes. \'Vest Conshohocken, PA:
London, United Kingdom: Thomas American Society for Testing and
Telford Limited (1973): p 73-80.
37. Queval, ].C., D. Combescure, Materials (1987).
T. Chaudat and P. Sollogoub. "Seismic 48. Curtin, \o\1.G., G. Shaw,J.K. Beck and

Behaviour of Reinforced Concrete G.I. Parkinson. Stmctuml Masonry
Structural \·Valls." Gtuie Pamsismique et Detailing. New York1 NY: Granada
RCponse D)'IUJflfiqiie des Oul'rages. Publishing (1984).
Vol. 2. Paris1 France: Association 49.1sberner, A.\·V. and L.R. Lauersdorf.
Fran~aise du Genie Parasismique "Preventive and Corrective
(1999): p 589-596. lvfaintenance Masonry." Tile
38. Duszek, M.K. and I~ Perzyna. "The Construction Specifier. Vol. 421 No. 9.
Localization of Plastic Deformation in Alexandria, VA: Construction
Thermoplastic SoHds. 11 lntemational
joumal of Solids and Structures. VoL 27, Specifications Institute (1989): p 84.

No. 11. Oxford, United Kingdom: SO. Catani, M.J. "Setting New Standards
Elsevier Science (1991): p 1419-1443. for Masonry." Tile Construction
39. Association l:ranp:~ise de Specifier. Vol. 42, No. 9. Alexandria,
Normalisation. Norme NF P/DTU
Hegles PS92, Reg/es Applicables aux VA: Construction Specifications
B{itiments. Paris, France; Association Institute (1989): p 108.
J.'ran~aise du Genie Parasismique 51. Jmpeclor~'> Guide for Concrete Masonry
Construction. TEK 132. Herndon, VA:
(1995).
40.1.fcMullen, P. "Evaluating Structural National Concrete Masonry
Association (1983).
and Thermal Components of the 52. Englekirk, R.E., G. C. Hart and the
Building Envelope.11 ASNT'l In(mretf Concrete Masonry Association of
Tllennography Topical Confi?rt'nce California and Nevada. Earthquake
Des(~n of Concrete Masomy Buildings,
!Cleveland, OH, June 19971.
Columbus, OH: American Society for Vol. 2. Upper Saddle River, NJ: Prentice
Nondestructive Testing (June 1997): Hall (1984).
p 155-165. 53. Guidelines fOr Specifying and Performing
41. Parekh, A. "Power Demand and Energy Infrared Impections, first edition.

Savings through Air Leakage Control Shelburne1 VT: Infraspection Institute
in High-Rise Residential Buildings in (1988).
Cold Climates." Thermal Performance of'
t!Je Exterior Etll'C'lopes ofBuildings V 54. Snell, J.R., Jr. and R.W. Spring.
[November 1992j. Atlanta, GA: 11 Developing Effective Operating

American Society of Heating, Structure and Procedures for a
Refrigerating and Air Conditioning Thermographic Inspection Program."
Engineers (1992).
42. 149-GP-2MP, Manual for Thermographic P!PM Tedmology. Vol. 6. Truckee, CA:
Analysis ofBuilding Enclosures. Ottawa, P/l'M Technology (June 1993).
55. Giedion, S. Space1 Time ami
Canada: Canadian General Standards Architecture, third edition. Cambridge,
Board (1986).
MA: Harvard University Press (1954).
43. 1997 ASHR4E Handbook- 56. Fielclen1 B.:vf. Conscrmtion of Historical
Fwrdamentals. Atlanta, GA: American
Buildings. London/ United Kingdom:
Society of IIeating, Refrigerating and Butterworth (1994).
Air Conditioning Engineers (1997). 57. \'Varren, G.J. Conserl'ation o(Brick.
44. ASTivf E 779-81, Measuring Air Leakase
by the Fan Pressurization Metlrod. West '·Voburn, 1·fA: Butterworth-Heinemann
(1999).
Conshohocken, PA: American Society
for Testing and rv1aterials (1981 ).
45. CAN/CGSR-149.15, Determination of
tile Ot'emil Em,l'lope Airtiglltne.~s o(
Buildings by tire Fall Pressurizatiou
Method Usins the Buildins\ Air llandli11g
S}lstems. Ottawa, Canada: Canadian

General Standards Board (1996).

Infrastructure and Conservation Applications of Infrared and Thermal Testing 655

58. Casarino, A., E. Costantino, 65. Cruciani Fabozzi, G., N. Ludwig,
N. Ludwig, L. Rosi1 E. Rosina, (i. <...i. Malchiodi and E. Rosina.
Stagno and E Vitali. "La "Non-Destructive Methods on P.:1lazzo
Manutenzione del rvfoderno: II Dm<J!e Ill Urbino: Thermal Analysis to
Determinate Not in Sight Holes.')
Monitoraggio del Calcestruzzo al
Quartiere Arle di Genova Stlllnlenwtiwwl Con(ert'IICC on
(] 980-1999)." Scienza e Bmi Culturali Non-lk~tructil'e Testing) Microanalytical
lv!et1wds and Etwiromnental Emlualim1
XV (Bressanone, Italy, July 1999!. for Study and Cometvation of lVorks of
Art: ART '96 (Budapest, Hungary,
Venice, Italy: Edizioni Arcadia Ricerche September 1996j. Brescia, Italy: Italian
(1999): p 533-542. Society for Nondestructive Testing
59. Vavi1ov, V., T. Kauppinen, E. Grinzato. (1996): p 211-219.
"Thermal Characterisation of Defects 66. Phillipson, 1vt. and A. Stu part.
"Temperature and i'vfoisture
in Building Envelopes Using Long Conditions in 1vfasonry: Frost
Performance." Intemalional S)'mposi11111
Square Pulse, and Slow Thermal \Vave 011 Moisture Problems in Building \Valls
Techniques." Researc/1 in Nondestructive [Porto, Portugal, September 1995].
Evaluation. Vol. 9. Columbus, OH: Porto/ Portugal: Vasco Peixoto de
American Society for Nondestructive Freitas and Victor Abrantes (1995):
p 405-415. '
Testing (1997): p 181-200. 67. Ljungberg, S.A. "Infrared Techniques
in Buildings and Structures: Operation
60. rvfaldague, X.P.V. and S. Marinetti. and .Maintenance." Infrared
"Pulse Phase Infrared Thermography." Metlwtlology mul Teclmology.
Langhorne, PA: Gordon and Breach
foumnl of Applied Physics. Vol. 79, Science Publishers (1995 ): p 21 1-252.
No. S. Melville, NY: American Institute 68. Chields, K.W., G.E. Courville and l'.\·V.
of Physics (1996): p 2694-2698. Chields. "An Investigation of Factors
61. Volinia, }vf. "Integration of Qualitative Influencing Infrared Roof ~vtoisture
Surveys Using a Mathematical Model."
and Quantitative Infrared Surveys to Tllermusense VI [Orlando, FL, April
Study the Plaster Conditions of 1983J. SPIE Proceedings, Vol. 446.
Valentino Castle.'' Tlu.mnoseuse XXII Bellingham, \·VA: International Society
[Orlando, FL, April 2000]. SI'IE for Optical Engineering (1983):
Proceedings, Vol. 4020. Bellingham, p 82-94.
\·VA: International Society for Optical 69. Seeber, S.A. "Use of Infrared
Engineering (2000): p 324-334. Thermography for the Identification
62. Grinzato1 E. "Stat<l deli'Arte sulle of Design and Construction Faults in
Tecniche Tennografiche per il Buildings." 'Jilamosense \11 !Orlando,
Controllo non Distruttivo e Principali fL, April 1983]. SPIE Proceedings, Vol.
Applicazioni.u Go11{erenza Nazionale 446. Bellingham, WA: International
PND~MD !Padua, Italy, September Society for Optical Engineering (1983):
p 56-63.
1997j. Vol. 1. Brescia, Italy: 70. Grinzato, E., V. Vavilov and
Associazione ltaliana Prove non T. Kauppinen. "Quantitative Infrared
Distruttive [Italian Society for Thermography in Buildings." Etu'ISY
and Buildings. Vol. 29. lvtanchestcr,
Nondestructive Testing] (1997): United Kingdom: Elsevier (1998).
p 130-152. 71. Buscher, K.A., \~'. \·Vild and
63. Bison, P., lvl. Dezzi Bardeschi, H. \.Yiggenhauser. "tvloisture
~·leasuremcnts in Building Materials by
E. Grinzato, T. Kauppinen, E. Hosina Amplitude-Densitive ivfodulation
and G. Tucci. "Infrared Thermal Thermography.'/ Diagnostic lmagitll'
Scanning: A ~vfethodology for Survey
1t:clmologics and Industrial Applicatiom
of Facades Palazzo della Ragione, pvlunich, Germany, june 1999). SPIE
Milan, Italy." I11emwseme X\f/11 Proceedings, Vol. 3827. Bellingham,
[Orlando, FL, April 1996]. SPIE \·VA: International Society for Optical
Proceedings, Vol. 2766. Bellingham, Engineering (1999): p 34-43.

V'-li\: International Society for Optical
Engineering (1996): p 55-64.

64. Grinzato, E., P. Bison, C. llressan and
A. lvfazzoldi. "NDE of Frescoes by

Infrared Thermography and Lateral
Heating." Qwmtitative Infrared
Thennosmplly (Qli?T '98) [September

1998]: Eurotherm Seminar 60. L6dz,
Poland: Institute of Electronics,

Technical University of Lodz, for
Association of Electrical Engineers,
Polish Committee of OptoElectronics

[2000[: p 64-67.

656 Infrared and Thermal Testing

72.Jenkins, D.R., L.I. Knab and R.G. 79. Bamberg, M. and C.). Shirtliffe.
Mathey. "Laboratory Studies of 11 lnfJuence of lvioisture and Moisture
Infrared Thermography in Ronfing Gradients on Heat Transfer through
Moisture Detection." Moistflre Porous Building :~vfaterials." Thermal
Misratimt itt Buildinss. Special Tm1ts111issim1 A4el1SllretneJJts o(
Technical Publications 779. \·Vest Insulation. Special Technical
Publication 660. \\1est Conshohocken,
Conshohocken, PA: American Society
for Testing and Materials (1982): PA: American Society for Testing and
p 207-220.
73. Ludwig, N. and E. Rosina. "~vfoisture Materials (1978): p 2!1-233.
80. Cruciani Fabozzi, G., V. Bestetti,
Detection through Thermograpl1ic
Measurements of Transpiration. D. Bevilacqua, A. Grossi, E. Rosina,
Tltermosense XIX lOrlando, FL, April S. Schiavetti and E.D. Ferrieri.
1997]. SPIE Proceedings, Vol. 3065.
Bellingham, WA: International Society "Castiglioni's Ivfanor: Analysis of the
Materials and of Their
for Optical Engineering (1997): Thermohygrometrical Status for the
p 78-86. Preservation Project." 6tlllntemational
Con(ermce APnD Applied to Cultural
74. Grinzato, E. and A. Mazzoldi. "Infrared Heritage: ART '99IRome, Italy, ·:rvfay
Detection of Moist Areas in 1999]. Rome, Italy: Assodazione

rvfonumental Buildings Based on JtaHana Prove non Distruttive fltalian
Thermal Inertia Analysis." Tilermosens!' Society for Nondestructive Testingj;
XI// [Orlando, FL, April 1991]. SPIE and lstituto Centrale del Restauro
Proceedings, Vol: 1467. BelHngham,
(1999): p 735-748.
\VA: International Society for Optkal 81. Cruciani-Fabozzi, G., E. Rosina and
Engineering (1991): p 75-82.
75. Vavilov, V.P., A.l. Ivanov and hL Valentini. "Thermography and
Gravimetric Tests ln Moisture
A.A. Sengulye. "Qualitative and Analysis." 20th National Conference o(
Quantitative Evaluation of Moisture in AlCJlT-GlCAT [Rome, Jtaly, December
1998]. Rome, Italy: Associazione
Thermal Insulation by Using Italiana di Calorimetria e Analisi
Thermography." 11wrmosense XIII
[Orlando, FL, April 1991]. SPIE Termica; Gruppo lnterdivisionale di
Proceedings, Vol. 1467. BeHingham, Calorimetria e Analisi Tennica.

\.YA: International Society for Optical 82. Maierhofer, C. and J. \'Vostmann.
Engineering (1991): p 230-234.
76. Grinzato, E., P.G. Rison, S. Marinetti "Investigation of Dielectric Properties
and V. Vavilov. ''Thermal/Infrared
of Brick Materials As a Function of
Non-Destructive Evaluation of ivfoisture and .Salt Content Using a
Moisture Content in Building: Theory Microwave Impulse Technique at Very
and Experiment." International High Frequencies." Non-Destructiw
Symposium: Dealing with Defects in Testing in Civil Eugilll'ering: ND'J:cE '97
Building [Varenna, Italy, September [Liverpool, United Kingdom, April
1994]. Milan, Italy: BE-MA (1994):
1997). Northampton, United
p 345-357. Kingdom: British Institute of
77. Grinzato, E., P. Bison, S. lvfarinetti and Non-Destructive Testing (1997):
p 743-754.
V. Vavilov. "Nondestructive Evaluation
of Delaminations in Fresco Plaster 83. Humphries, H. "Infrared Testing in Art
Conservation." Materials Emltwtiml.
Using Transient Infrared
Thermography." Research bz Vol. 45, No. 4. Columbus, OH:
Nondestructil'e Emluation. Vol. 5, No. 4. American Society for Nondestructive
Columbus, OH: American Society for
Testing (April 1987): p 426-428, 430.
Nondestructive Testing (1994): 84. Livingston, ItA. "Transferring
p 257-274.
Technology from Conservation
78. Rosina, E., N. Ludwig and L. Rosi. Science to Infrastructure Renewal."
110ptimal Conditions to Detect Electronic publication. Public Roads.
Vol. 58, No. 1. IvfcLean, VA:
Moisture in Ancient Buildings: Study
Cases from Northern ltaly. 11 Turner-Fairbank Highway Research
Thermosense XX [Orlando, FL, April Center (Summer 1994).
1998]. SPIE Proceedings, Vol. 3361.
85. Alexopoulou, A., Y. Chryssoulakis and
Bellingham, \\1A: International Society j.-}d. Chassery. "Infrared Image
for Optical Engineering (1998):
Processing Techniques Applied to
p 188-199.
Works of Art." Proceedings of tile 12th
\·Vorld Conference on Non-Destructive

Testing !Amsterdam, Netherlands,
April 1989j. Vol. 1. Amsterdam,
Netherlands: Elsevier (1989}:
p 515-517.

Infrastructure and Conservation Applications of Infrared and Thermal Testing 657

86. Eastaugh, N. "Examination of 97. Mansfield, j.R., M.G. Sowa, C. ~·fajzels,

Paintings by Infra-Red and Other C. Collins, E. Cloutis and H.H.
Mantsch. "Near Infrared Spectroscopic
Techniques.'' Digest No. 1995/115 Reflectance Imaging: Supervised vs.
Unsupervised Analysis Using an Art
!Colloquium ot Science, Education
Conservation Application." Vibrational
and Technology Division, London, Spectroscopy. Vol. 19, No. 1.

United Kingdom, May 1995]. London, Amsterdam, Netherlands: Elsevier
Science (February 1999): p 33-45.
United Kingdom: Institute of Electrical
98. Henry, E.B., C.M. Stuart and
Engineers (1995): p 6-1-6·3. \·V. Tomasulo. "Metal and Alloy
Identification." Nondestructive Tcsti11g
87. \"lest, L. 11 Face Lift at St. Peter's Handbook, second edition: Vol. 9,
Special Nondestructive Testing Methods.
Cathedral." InfraMation. Vol. 1, Issue 3. Columbus, OH: American Society for
Nondestructive Testing (February
North Billerica, MA: Infrared Training 1995): p 367.

Center (April 2000): p I, 3.

88. Van Asperen de Boer, j.R.j. "Infrared

Reflectography: A Contribution to the

Examination of Earlier European

Paintings." Dissertation. Amsterdam,

Netherlands: University of Amsterdam

Guly !970): p 11-15.

89. Real, W.A. "Exploring New

Applications for Infrared

Reflectography. 11 Bulletin of tile

Cleveland Museum ofArt. Vol. 72,

No. 8. Cleveland, OH: Cleveland

Museum of Art (December 1985):

p 392-411.

90. Ainsworth, M. Interview Qanuary

1987).

9]. Bell, T.E. "Seeing into the Past.11

Connoisseur. Vol. 210, No. 844. New

York, NY: College Art Association

aune 1982): p 140-141.

92. \.Yheelock, Arthur K., Jr. "NEA FeHows'

Diary: Vermeer's Painting Technique."

Art journal. Vol. 41, No.2. New York1
NY: Hearst Corporation (Summer

1981): p 162-164.

93. Porter, D. Correspondence Uanuary

1987).

94. Bacci, M., S. Haronti, A. Casini,

F. Lotti, M. Picollo and 0. Casazza.

''Non-Destructive Spectroscopic

Investigations on Paintings Using

Optical Fibers. 1 1\4aterials Issues in Art
'

and Archaeology Ill [San Francisco, CA,

April-May 1992]. Materials Research

Society Symposium Proceedings,

Vol. 267. Pittsburgh, PA: 1vfaterials

Research Society (1992): p 265-283.

95. Clark, R.j.H., P.j. Gibbs, K.R. Seddon,

N.M. Brovenko and Y.A. Petrosyan.

''Non-Destructive in Situ identification

of Cinnabar on Ancient Chinese

·Manuscripts." joumal of Raman

Spectroscopy. Vol. 28, Nos. 2-3. Bognar

Regis, \.Yest Sussex, United Kingdom:

john Wiley and Sons (February !997):

p 91-94.

96. Baronti, S., A. Casini, F. Lotti and

S. Porcinai. "Multispectral Imaging

System for the "h•fapping of Pigments

in \·Yorks of Art by Use of

Principal-Component Analysis.~~

Applied Optics. Vol. 37, No. R.

VVashington, DC: Optical Society of

America (March 1998): p !299-1309.

658 Infrared and Thermal Testing

CHAPTER

Infrared Thermography of
Electronic Components

Bo Wallin, FUR Systems AB, Danderyd, Sweden
(Parts 1 and 2)
Boguslaw Wiecek, Technical University of L6dz,
Institute of Electronics, L6dz, Poland (Parts 3 and 4)

PART 1. Temperature Measurement of
Electronic Components

\'\1ith the availability of a commercial nonunifonnly in the object. Only if the
thermographic camera system in 1965, emissivity and the reflected ambient
thermography became an important tool temperature in each point of the object
for quality control of electronic are known, can its true temperatures also
components. Since then thermographic be measured.
techniques for electronics have been
developed. Noncontact measurement has One way of making the emissivity
shown its applicability for measuring the uniform over the object is to paint the
true temperatures on components like object with some high emissivity paint,
printed circuit boards, hybrids and thereby making the measurement easier.
microcircuits.l·2 However, there are at least two good
reasons for avoiding such techniques. The
To measure true temperatures it is first reason is that painting might destroy
necessary to understand not only the the object; the second is that it changes
virtues but also the limitations of this the radiation properties of the object.
measurement technique. The physical Thus the object will be a better radiator. It
background must be understood to
develop relevant techniques. This will dissipate more ener&1-' and stay at a
application demands a complete
measurement solution, including the lower working temperature, which might
proper hardware tailored to this lead to a thermal design that gives the
application and software necessary for designer incorrect information.
processing the thermograms acquired
with this hardware. Temperature Measurement
on Printed Circuit Boards
Measurement techniques must be
adapted to test objects. Looking at a Printed circuit board components are
printed circuit board is different from normally made of materials ·with strongly
using a microscope to look at varying radiation properties. From a
microcircuits or objects measuring a few thermographic point of view the printed
square centimeter, such as hybrids and circuit board surface is built up by a large
surface mounted devices. number of points. Each of these points
might have another emissivity value. The
Delow, a technique is described that calculation of the temperature must
makes it possible to measure true therefore take the individual emissivity in
temperatures, even of objects hidden from each point of the image into
direct measurement ·while sitting in a rack consideration. For example, the emissivity
or box. over one arbitrary printed circuit board
varied from 0.13 to 0.93.
Temperature Measurement
Figure 1 shows a measurement setup.
In noncontact temperature measurement Note that the distance between the object
it is possible to calculate the correct object
temperature provided the object FiGURE 1: Setup for temperature measurement on printed
emissivity, the ambient temperature and circuit boards.
the atmospheric temperature are known.
Electronic components are generally made
of various materials such as metal,
graphite and plastics. It should always be
assumed that the emissivity varies from
point to point over the object.

Furthermore, the setup for this J..;ind of
measurement with the thermal camera
close to the object usually makes it
necessary to perform calculations in the
pre.~ence of varying reflected ambient
temperature over the object, because the
camera itself is reflected in the object. A
working camera shows a nonuniform heat
pattern, so it will be reflected

660 Infrared and Thermal Testing

and the camera is about 1 m (40 in.). A !Jiack and hence cold looking componenb
wider fidd of view would let the camera at 5P03 and SP04. The printed circuit
come closer to the object. On the other hoard contact under SPOS is not powered
hand a closer range would create more up but has obviously been heated to the
geometrical distortion in the image. same tempcratme as the board itself.
A 20 degree lens at about 1 m (40 in.)
distance will usually give a good result for Figure 2b shows exactly the same
printed circuit boards of European size. It object after emissivity correction. The cold
will also diminish the camera's influence looking parts at the top ll0\\7 have a
on the reflected ambient temperature. higher temperature, obviously from
applying the correct emissivities.

How to Measure True Finding of Emissivities in
Temperatures on Objects Each Point of Object
with Different Emissivities
The true temperatures on complex objects
The true temperatures can be calculated can be found only in controlled
only if a technique is used that can measurement u mditions. The individual
handle the variation of the emissivities emissivity in each point of the object is
over the object. Such a process ran he calculated by means of a n•(erencc imase.
t·alled eqttalization, meaning that the One way to obtain such an image is to
thermal image of an object can be
recalculated to a situation where the FIGURE 3. Equalization box: (a) cross section; (b) sliding lid
object can be considered to have only one drawn off box.
emissivity value. This recalculation can be
done if the emissivity is known in each (a)
point of the object. After recalculation,
this knowledge will help find the true Printed circuit board
temperatures of the object.
~ Airflow
So the problem is to measure the
emissivity in each point of the object, J'=~=_}==~;: '_ ."':He~~t~_"9_'_''_ment_'____ ,_ _ __
that is, to create an emissivity map of the
object. The values of this emissivity map L _________"_"_'_'"-"_.,,_ti~---·-----_j
are then used to calculate the correct, true
temperatures over the object. (b)

Figure 2a shows a thermogram of the
control board of a hard disk before
emissivity correction is applied. Note the

FIGURE 2. Printed circuit board, powered up: (a) before
emissivity correction: (b) after emissivity correction applied.

(a)

(b) Mirror plate Slidable lid

Infrared Thermography of Electronic Components 661

put the printed circuit board into an Therefore neither the object nor the
insulated box, an equalization box, where camera may be moved from the moment
it can be heated up uniformly (see Fig. 3). when the reference image is captured
until the last real image of the printed
The objective is to heat up the whole circuit board to be tested has been
object as equally as possible to a captured. The printed circuit board and
the infrared camera must stay in the same
temperature of, say, 323 K (50 oc = positions during all measurements.

122 °F). This temperature is not crucial Equalization Boxes
but should be above ambient (293 K
120 'C = 68 'FJ) and preferably close to the Equalization boxes have been designed
expected working temperature of the and manufactmed. Such a box is shown
object. in Fig. 5.

The reflections should come FIGURE 5. Equalization box: (a) with lid dosed, measuring 473
exclusively from the surroundings x 220 x 310 mm (18.9 x 8.9 x 12.4 in.); (b) from behind with
(ambient) to the hox. Therefore the lid opened to show printed circuit board mounted in box.
slanted walls are made of polished (a)
aluminum, which has a very low
emissivity. Its high reflectivity will then (b)
reflect the ambient (low) temperature
from the room rather than the high
temperature from the sliding lid-or the
mirror plates themselves.

\·Vhen the wanted reference
temperature is reached the lid is quickly
drawn off the box and the reference
thermogram is captured.

From the reference thermogram it is
possible to calculate the emissivity in each
individual point. The image in Fig. 4
includes an emissivity chart, ·where the
emissivity values (multiplied 100x) are
shown in a few spots. As can be seen SP03
and SP04 have very low emissivity values.
This is also the reason for the low
apparent temperatures in Fig. 2a. The
emissivity value used for calculating the
temperatures was incorrect.

The software program uses the
emissivity map to calculate the
temperatures in the corrected image,
which displays the true temperatures of
the object. It is important that the
reference image and the images to be
corrected cover each other exactly.

FIGURE 4. Emissivity chart showing emissivity values in image.

IR-1 EMRefl

SP01 91.1

SP02 7,5

SP03 23.0

SP04 03,8

SP05 84.2

662 Infrared and Thermal Testing

Thermographic equalization was
already being implemented in the 1980s.
Today's powerful computers make it
possible to pron:·ss such an image in
about 1 s. As the inspection usually
generates quite long sequer'Kes of raw
images, equalization must be able to
process these sequences automatically.

There seems to be no comparable,
noninvasive technique <lvailable for
temperature measurement on printed
circuit boards. l-Ienee equalization is an
i11evitable tool for correct temperature
measurement on electronic components.
Long experience of the technique has fine
tuned the man-to-machine interface so
that it is quick and easy to handle. Once
the reference images arc captured the rest
can be handed over to the system.

Infrared Thermography of Electronic Components 663

PART 2. Temperature Measurement with
Infrared Microscope

1vteasurement with a microscope needs a to the object surface. This can usually be
more developed equalization technique.:l done hy putting a smi:lll dot of paint \Yith
The emissivity certainly varies over the a known emissivity on the object. The
object ~as in the example with the temperature difference between the
printed circuit board. Figure 6 shows a heating stage and the surface of the object
thermal microscope. can be one or a few degrees, so it is
important to know the real temperature
The microscope itself is a dominant of the object.
part of the object's cmzbintce. The object is
very small, in this case about 6 x 3 mm Comprehensive software for this kind
(0.24 x 0.12 in.). The distance between of thermographic measurement includes a
the front lens of the microscope and the presentation of the image in real time as
well as a presentation of the equalized
object is about 25 mm (l.O in.). The image in at least quasi real time. This
microscope has its working temperature, makes it possible for the operator to
which might be a few degrees above control the geometrical setting (focusing)
ambient. Jf the object is shiny, \Vhich is so of the object during the actual
often the case with chips, tlle very cold measmement. Simultaneously it is
detector can see itself- that is, there will possible to follow the development of the
be a very cold spot h1 the middle of the thermal situation in a twe temperature
image.
imnge. This is called the narcissus effect.
In this case the emissivity as -..veil as the If the test strives for the highest
possible time resolution it should also be
reflected ambient temperature both vary possible to perform equalization
from point to point, so it is necessary to aftenvards as a postprocessing operation.
c<tlculate with two unknowns. Hence two A practical technique for microscopic
reference thermograms at different measurement might then look like the
temperatures need be captured. The object follO\\'ing:
has to be heated up to two different
reference temperatures - for example, 1. Put the object on the heating stage.
60 degrees and 80 degrees- because it is 2. Localize the object and bring it into
necessary to create two different cases. To
do that the object has to be fixed in a focus.
ltcatiug stage, that is, some device that can 3. Activate the equalization function.
give the object these two different 4. Power up the heating stage to the first
temperatures in a controlled way.
temperature.
The heat transfer between the heating S. \'\1hen the first reference temperature
stage and the object usually takes place
via comluction. 1t is therefore important is reached capture the first reference
that the operator check the real image and store it. Re careful \'l'ith the
temperature of the object while the name of the image so that they can be
temperature falls from the heating stage identified afterwards, for example,
ref60.
FIGURE 6. Diagram of thermal microscope. 6. Set the heating stage to the second
reference temperature and capture a
Mirror corresponding reference image. Name
it , for example, re(SO.
·-- 7. Let the heating stage cool down for
the measurement session.
@ 8. \'\'hen the wanted heating ~tage
temperature is reached power up the
Magnifying lenm --------------- object with the wanted voltage and
current.
Signal output 9. Capture one or more thernwgrams of
the object under pu·wer.

If a whole healing process is to be
studied, then a whole sequence with the
wanted speed should be captured.
Activate the equalization function to get
the quasi real time trw.' temperature
image onto the screen. The software
should allow the processing to he carried

664 Infrared and Thermal Testing

out automatically, ending up in a total field of view is about 6 x 3 mm
sequence of stored, true temperature (0.24 x 0.12 in.) and the active part of the
images. object !s about 1.4 x 0.45 mm
(0.06 x 0.02 in.).
When this sequence has been
performed, the result may look as in Practical Measurement on
Fig. 7. This series of images shows that the Printed Circuit Board
true temperatures of the chip at 5 V and Sitting in Rack
I A load (Fig. 7c) are considerably higher
than they seem to be in Fig. 7d. From the One requirement of noncontact
reference images it can be seen that the temperature measurement by
emissivities vary a lot over the image. The thermographic imaging is that the object
must be seen by the infrared camera. This
FIGURE 7. Reference images for stages of microscopic necessity, unfortunately, makes it difficult
measurement: (a) reference image at 352 K(79 oc = 174 °F); to study the temperature distribution on a
(b) reference image at 334.1 K(60.9 oc = 141.6 oF); printed circuit board in its normal
(c) circuit being powered up, image not yet equalized; environment. However, there is a
(d) equalized, true temperature image. technique that works in many situations.
Consider the exponential cooling curve in
(a) Fig. 8.

(b) Figure 8 shows the normal cooling
curve for an arbitrary component. The
idea is to determine the time constant for
each point in the image and then apply
that to the images taken at times t1 and t2•
It is then possible to extrapolate
backwards to find the image at t0 , when
the object was still hidden from the
thermal camera.

The sequence in Fig. 9 illustrates the
principle that an object adapts itself to a
new ambient temperature along an
exponential curve. The first image at
time t0 (Fig. 9a) has been calculated from
the images taken at times t1 (Fig. 9b) and
t2 (Fig. 9c). The technique is as follo\vs:

FIGURE 8. Cooling curve for component on printed circuit
board.
(c)

(d) ,, ,,

Time (arbitrary moments)

legend
u = observation angle (at specified moment)

T~,,b =ambient temperature
To!>J = temperature of test object

t -=- time (arbitrary points)
10 "' time at moment 0
11 = time at moment 1
!2 = tin1e at moment 2

Infrared Thermography of Electronic Components 665

1. Let the printed circuit board heat up backwards by means of its individual
and reach its normal operating cooling time constant. Different
temperature in the rack. components have different cooling off
time constants, so they must therefore be
2. Switch Off the power, take out the calculated individually.
printed circuit board and put it into
an equalization box. At power off After the extrapolation procedure is
capture the first thermogram. It will carried out the normal equalization has to
show nothing of interest but will take place and results in a true
capture the time for power off. temperature thermogram of the hidden
object at pO\\'er+off time. That has been
\Vhen the printed circuit board is fixed done in the pictures shown in Fig. 9.
to its place in the box, start capturing a
sequence which lasts two to three times
the time between power off and the
capture of the second image.

Ilaving stored the two images, nm the
program for extrapolation backwards and
find the restored first image. This image
represents the thermal picture of the
object when it was still in its rack. Every
point in that image has been extrapolated

FIGURE 9. Printed circuit board cooling to ambient
temperature: (a) at power oft, timet= 0; (b) 19 s after
power off; (c) 50s after power off.

(a)

(b)

(c)

666 Infrared and Thermal Testing

PART 3. Emissivity Evaluation for Electronic
Circuits and Components

Introduction detector in the camera: 2 to 5.6 pm for
short wavelength detectors; 8 to 12 pm
A persistent challenge in thermographic for long wavelength detectors.
measurement is correction of temperature
readout according to emissivity of the To evaluate the incident flux, the
investigated object. In electronics where infrared mirror in the form of a highly
there are many clements with different polished copper plate with reflection
emissivities (epoxy substrates, metals and factor about 0.98 is used. One assumes
ceramics) the correction of thermographic independence of the emissivity and
images by assuming homogenous reflectivity from the wavelength in the
emissivity may lead to misinterpretation spectral ranges mentioned above.
of measurements. The problem of
emissivity measurement will exist as long fiGURE 10. Measurement of flux: (a) incident flux;
as thermography does. There are some (b) reflected flux. Infrared mirror has emissivity close to zero.
techniques that permit measurement of
emissivity values. The calorimetric (a) Infrared c<Jmera
technique is well explored. It is based on
measuring radiation flux while the Heilt source
temperature of the material is known.
Below, an indirect approach of measuring
emissivity is mentioned, where reflectivity
is used to measure emissive energy.

Principle of Reflection Infrared mirror
Technique
(b) Infrared camera
The behavior of electromagnetic waves on
the border of two bodies can be Heat source
described:'1
Object under measurement
(1) A + 11 + T
legend
where A = absorbed energy, R = reflected
energy and T = transmitted enert,')'. f.,"",!> =- energy density emitted by environment
Figure 10 shows test setups for f"'' = incident energy density
measurement of incident and reflected
flux. £m:, = emis5ivity of infrared mirror (do5e to zero)
F,.t.1= emis5ivity of object
Some opaque objects have
transparency equal to zero. For radiation
parameters independent from the
wavelength, emissivity cis expressed as:

(2) E ~ 1 - p

where p is reflectivity.
For objects in ambient temperature it is

possible to evaluate emissivity on the
basis of ine<Jsurements of the incident and
reflected energy.

One aim for developing the technique
for emissivity measurement is to use the
same infrared camera used to measure the
temperature. To evaluate total
hemispherical emissivity, the heat source
has to emit the radiation that totally
covers the spectral range of the infrared

Infrared Thermography of Electronic Components 667

A set of metal bodies (aluminum and The reflected flux including power
iron) with different surface states was emitted by investigated body in ambient
prepared to verify the accuracy of the temperature can he expressed as:
tedulique described below. The emissivity
factor for each body was evaluated
calorimetrically.5,6 Obtained values of
emissivity vary from 0.25 to 0.45.

Emissivity Evaluation for where c is <tn unknown emissivity and 1~n
Specular Surfaces is a substitute temperature obtained from
the camera.
Measurements of the emissivity are based
on the assumption that reflection nnally, the value of emissivity can be
characteristics for specularly reflecting calculated as:
surfaces (such as well polished metals) is
very sharp- that is, a very small (6)
deviation from the mirror angle causes
very rapid decrease of the reflectivity. This In many practical cases for diffusely
sharpness means that the main part of the reflecting surfaces, the values of emissivity
flux is reflected in the mirror angle. In obtained using Eq. 6 are incorrect because
consequence it is possible to evaluate the only that part of the enerb'Y reflected in
emissivity on the basis of specular the mirror angle has been measured.
reflectivity. Emissivity strongly depends on surface
conditions. In many practical cases there
For an infrared mirror in ambient is a difference between emissivities
temperature, the flux measured by camera measured according to Eq. 6 and results
takes the form: presented in the literature.5·8

where Einc is incident flux, Tcu is copper
mirror substitute temperature, 7~ is
ambient temperature and Pcu is copper
mirror reflectivity:

FIGURE 11. Reflectivity characteristics of real body (representative metal) for different angles of
incident flux.

Ref!ectivily P1.~N

legend
jJ =angle of incident flux
q =angle of reflective flux
p = reflectivity
t = trammissivlty

668 Infrared and Thermal Testing

Emissivity Evaluation for reflection that exists in many practical
Diffuse Surfaces cases. To take this phenomenon into
account the measurements have to be
As mentioned above, the assumptions on made in different directions,
the mirror reflection is sometime not
valid, even in the case of metal bodies. Evaluation of Emissivity
The state of the surface of the investigated with Anisotropy of
body (mainly its roughness) is the main Reflection
factor that can change the emissivity. The
diffused reflection has to be taken into The analysis of errors in particular
account in many practical cases:P) The measurements of emissivity using the
reflectivity characteristic for a technique described here has led to the
representative metal object is shown in conclusion that reflectivity characteristics
Fig. 11. sometimes depend on angle of
observation. Such anisotropy effects have
For the object with given emissivity, been observed for samples with distinct
the total reflected energy is equal to texture on their surface. If one of the
(1 ~f.)Eino where Einc is incident cncq,')'. directions on the surface of the sample is
The mirrored reflection is sharper and the marked out (for example in the mat
more diffuse reflection is flatter. As shown process), the reflectivity characteristic in
ii1 Fig. 11, the correlation between the that direction will differ significantly from
valne of flux reflected in the mirror angle the characteristic measured in the
and a certain a parameter describing the perpendicular direction (Fig. 13).
characteristic width is expected. As such a
parameter, coefficient 0 is chosen as a In Fig. 13 the variable ~<1> represents
deviation from mirror angle and the value
ratio of reflected flux for angle p (different of the reflected energy E is expressed in
scaled units:
than mirror one) to the flux reflected for
(10) E[/TJ
the mirror angle Pmir-
To continue the evaluation of The total value of the reflected energy
is proportional to the volume of the solid
emissivity, the heat fluxes must be limited by the shapes of the reflectivity
measured as follows: (1) for an infrared
mirror and mirror angle, (2) for a given FIGURE 12. Correlation curve of reflected flux in mirror angle
object and mirror angle and (3) for a
given object and the angle deviated from and parameter 0 defining shape of reflectivity characteristics.
the mirror one,
Real emissivity of aluminum and iron samples has been
The relative value of the energy K evaluated calorimetrically. Rectangles indicate range of
reflected in the mirror angle has been results considering accuracy of measurements and
introduced as: environmental noise.

(7) K cr7~~ - Ea

aT~11 - Ea

where Ea = a'l~4, Hnally:

(8) ym4 - Ta"mb

T C4u - T 4

amb

The parameter 0 of the shape of the
reflection characteristic is defined as:

(9) s 12

0.2 'o::J

0.1

where Til is substitute temperature (K) 0 0.1 0.2 0.3 0.4

measured for angle p, 1~n is mirror legend
I to 5. A!t,minum, emissivity t: "'0.31 to 0.35
angle temperature (K), 7~ is ambient 6. Iron, emissivity£=- 0.44 to 0.51
temperature (K) and Tcu is substitute
temperature (K) for infrared mirror 7 and 8. Iron, emissivity£"' 0.36 to 0.42
9. Aluminum, emissivity F = 0.45 to 0.49
defining heat source temperature. Results 10. Aluminum, emis5ivity F ==- 0.4 to 0.45
of the measurements are shown in Fig. 12. 11. Aluminum, emissivity c == 0.32 to 0.38
12. !ron, emissivity r ,_ 0.44 to 0.5
The nonlinearity of the correlation
curve can he noticed in Fig. 12. Some of

the results differ significantly from
obtained results. The technique presented
above does not consider anisotropy of the

Infrared Thermography of Electronic Components 669

characteristics for all directions of calculate the volume of such a solid, the
observation. It is quite difficult to measure assumption that the cross sections of the
total hemispherical reflectivity, so some reflectivity characteristic.~ nre elliptical is
simplifications have to be made. To introduced. To check the correctness of
this assumption, the cross section of the
FtGURE 13. Reflectivity characteristics for one sample with hemispherical reflectivity characteristics
anisotropy on surface for two perpendicular directions of have been measured for a metal sample
observations, radiation flux versus angle for two (l'ig. J4).
perpendicular directions.
The cross sections shown in Fig. 14
100 have been obtained from characteristics of
reflectivity measured in different angles u
90 of observation (a1, a 2, a 3) in the range
from 0 to 90 degrees. The change of the
80 observation angle has been obtained by
rotating the sample about a given angle.
g 70 For each rotation angle, the reflectivity
characteristic E UTI =/(!>.$)has been
~ 60 measured and then the shapes
corresponding to equal values of energy
:f 50 have been drawn.
w 40
~ The assumption of the ellipsoidal shape
~ 30 of the cross section is not valid in the case
of the samples with very high anisotropy.
20 It leads to the errors in calculations of the

10 FIGURE 15. Temperature map of converter from left side: two
diodes placed on radiators, transformer and resistive load:
O L __ __ L_ _~----~~~===-+ (a) before covering with black paint of emissivity£~ 1.0;
(b) after painting.
0 5 10 15 20
(a)
U<l' (degrees)

legend

t\cf> =for first direction, angle between camera axis and norma! to object
E01) ""characteristic of reflectivity
"*-=direction 0 degrees
-II-= direction 90 degrees

FIGURE 14. Cross sections of hemispherical reflectivity
characteristic for sample with anisotropy on surface.

40

30 (b)
-~

i"

:"w3' 20

6

<l

10

0
0 2 3 4 56 7 8

.0.1112 (degrees)

legend
.0,(])1 =for first direction, angle between ram era axis and normal to object
.0.cf>2 =for second direction, angle between (amera axis and normal to
object
•=f=30JT
ee£e40JT
.1..=£=50)1
+e£e60JT
C =observation angle (t = 60 degrees
0 =observation angle (( = 45 degrees

i::J..= observation angle u = 30 degrees

670 Infrared and Thermal Testing

total reflected energy and hence of the placed on the black painted radiator.
solid volume. An additional problem is Transistors work in the final stage of the
how to choose the directions of
measurements properly. 100 W power supply (Fig. 16).
Emissivity of all these elements h<Js
To check correctness of the proposed
technique some measurements for been measured with the reflection
different samples have been made. The technique. The results in ·n1ble 1 take into
results have been compared with the ones account the accuracy of the measurement.
obtained by calorimetry and by equalizing
the emissivity by painting the surface Temperature maps for both objects has
with highly emissive coatings. been corrected. To verify the results the
second series of the measurements in the
Emissivity Correction in same conditions have been made after
Thermo~raphy of covering all the elements with bl<Jck paint
Electromc Circuits (£ ~ 0.9).

Two power electronic circuits have been TABLE 1. Measurements of emissivity using
measured using the technique described reflection technique.
above. The first one is presented by
thermal images in Fig. 15. It consists of Test Object Emissivity
rectifier diodes on the metal radiator,
transformer and resistive load. The second Metal radiator of diodes 0.3 to 0.4
circuit consists of a pair of power
transistors (laser diodes in a metal case) Case of transistors 0.3 to 0.4

fiGURE 16. Temperature map of converter after correction of Transformer and resistive load 0.9 to 1.0
emissivity: (a) emissivity£~ 0.3; (b) emissivity E ~ 0.4.
FIGURE 17. Temperature map of power transistors in end
(a) stage of power supply unit (1 0 V, 10 A): (a) before covering
with black paint of emissivity E ~ 1.0; (b) after painting.

(a)

(b) (b)

Infrared Thermography of Electronic Components 671

Thermographic measurements of the (Fig. 18}. Because of the comple-x shapl'
power converter ·without emissivity and many small details in the observed
correction suggest that the most heated object, the results are not as
parts of the circuit are the resistive load straightforward as in the previous case.
and diodes and that the transformer has a Additionally, the parasitic reflection
much lower temperature {Hg. 15a). After occurs, which is more important for an
covering all the elements with black paint object of low emissivity. Nevertheless, the
(E "" 1) it can be seen that the diode has evaluation of emissivity t from 0.3 to 0.4
the highest temperature (Fig. 15b), gives signifh:zmt improvement of the
temperature measurements.
Figure 16 shm\'S the temperature map
after correction using the measured values Conclusions
of the emissivity.
A technique has been developed for
Figure 17a shows the temperature map practical applications of emissivity
of the final stage of the power supply (two evaluation. The technique gives good
power transistors placed on same results in the laboratory, where the
radiator). The situation seems to be measurements can he done precisely and
paradoxical: the heat source has a lower with good equipment. Two problems limit
temperature than the cooling fins. A real the technique: (1) difficulty in very
temperature map obtained after painting precise determination of the mirror angle;
the object is shown in Fig. 17b. On lhe {2} parasitic reflections from objects with
basis of the measurements of the complex shapes and low emissivity.
emissivity for the transistor enclosures,
the temperature has been corrected This technique can be a good basis for
classifying the objects for ones with high
FIGURE 18. Temperature map of power supply unit after (£ "" 0.9) and low(£ "" 0.3) emissivity. The
correction of emissivity factor of upper side of transistors: technique can be useful when the correct
(a) emissivity £ = 0.3; (b) emissivity£= 0.4. interpretation of the thermal state of the
device (for example failure analysis) is
(a) needed rather than the measurements of
the temperature with very high accuracy.
The technique presented can be also used
in the case of working circuits (devices)~
for example, with high voltage but with
the assumption that energy emitted by a
part of the circuit is small in comparison
with the total energy reflected from its
surface.

(b)

672 Infrared and Thermal Testing

PART 4. Spectral Emissivity Evaluation of
Materials for Microelectronics

Introduction various spectral ranges. Spectrc:1l emissivity

Emissivity is measured for materials used may be useful for calculating heat
in electronics -for example, aluminum, removal by radiation in microelectronic
semiconductors {silicon and germanium)
and diamondlike thin structures such as devices. Emissivity needs to be evaluated
coatings. Additionally, emissivity needs to whenever thermography is used to
be evaluated for semitransparent and measure temperature. Emissivity depends
multilayered dielectric materials. The
measurement is performed using infrared on many varying parameters:
spectrometry. For every sample the temper(lture, wavelength, surface
reflected and transmitted energy are oxidization, roughness etc. Although
measured in the direction normal to the there are various techniques to measure
surface of the investigated material for emissivity, it is hard to quantify emissivity
precisely.5•6

For opaque materials the directional
emissivity can be evaluated:

FIGURE 19. Reflectivity and emissivity for aluminum in band from 2.5 to 14 f-Jffi: (a) unpolished aluminum; (b) aluminum with
diamondlike coating; (c) anodized aluminum, black; (d) anodized aluminum, not black.

~: -~1--=-=~±=L(a) 10,----~--- .-t_l----=- ----t----:J (c) 1.0
Ifl - 0.9
p" 0.8

r_- _:-:: -_- j- ___--1_--:_t~ .r-- '-- _I :~

o.51- ~--0 _I - -~ 0.7
--'_ t-----·~_.-- f--.-- c-[ 0.6
. 4 1 -+ c 0.5
0.4
b" O

"0 -~

oc "0

a_

-ij~~~'--~+-----, .=c_i -L :ep 0.3
0.2
~ 1 I - f->-~-:_:~~-t ::-:-)~ .::-:: :__;-I •'\; 0.1
"" 0
24 6 8 10 12 14 16 2 4 6 8 10 12 14 16

Wavelength ), (!-lm) Wavelength }, (!-lm)

rl{b) (d)
----~--~ - ~1- T~:~ ~---~(f~--- ; .. _ j1.0
~:1.0 I- ~ _r_ ~-~_:-]
i l··-··0.9 +-H-j'i· .... _
1
~- ~~---1- -f-- -r:: -:-- _J_ -1 0.8 - · - - -
I I

-~
--! - -0.7 '- - - '-'e·-- , - I
+-0.6 L - ;~ --~:: --~:
r_- -_:~ _t_ 1- -1 -i-_r 0.5 ~- ..
1
I +-r-a_ -iI - 0.41- -~~-- -~-_j_
03 . i - -L- j
I0.2 _, _ J. _I_ J!_ . : 0.3 i IIII -
o.1
-t- I1 , 0.21 r
o
I0.1 II
2 4 6 8 10 12 14 16 j _0 (___
- _ _ '__ j

Wavelength ).. (I-'m) 2 4 6 8 10 12 14 16

Wavelength A (jJm)

legend

-=reflection
.... ==emission

Infrared Thermography of Electronic Components 673

(11) e(e) ~ 1 - p(e) Emissivity Measurements

where p(9) denotes directional reflectivity The rt"sulb of the reflection and
for angle 9. For metals, the emissivity transmission measurements and the
strongly depends on the optical properties calculated emission are presented in
of each metal, especially on the reflective Figs. J9 to 23. Aluminum samples with
index typically expressed as a complex different surface conditions and
number 11: semiconductors (silicon and germanium
covered by thin diamondlike layers) were
(12) II ~ 11' + ik' chosen for measurements. All
measurements were done in a direction
The problem is much more difficult for normal to the surface of investigated
semitransparent and multilayer structures body, in the spectral range from 1.4 to
in microelectronics. To evaluate the 14 pm.
emissivity of such structures, material
transmission and internal reflections must For opaque materials like aluminum
be considered.5 The electromagnetic ·wave the normal spectral emissivity is
propagation theory is widely applied in calculated:
such cases, especially for dielectric layers
with a thickness of the same order as the where p11 (),) denotes the normal spectral
waveleng'th. reflectivity. For semitransparent

FIGURE 20. Reflectivity and transmissivity for silicon in band fiGURE 21. Reflectivity and transmissivity for germanium
from 2.5 to 14 ~m: (a) silicon; (b) silicon with diamondlike from 2.5 to 14 11m: (a) germanium; (b) germanium with
diamondlike coating.
coating.

(a) (a)

0.7 ::r·1~t~ ~tr~
.13~

JsH~r: -r~l!:i:f 0.6

o.s -1 -I- 1-!- 1

c ~----l'\1)-~--)1-- I f-0.3
~~
0.4 -- -_j_
~o

"U 'OJ
cm
m'o 0.3 t- T0.2 -1
0.2
a. - ---' -:
0.1 l T L Ii0.1 -!-
.·.,~ _j
0 L..
v

~

··~-~r:[i·t~'tj

~
__L~-' _j_ j__j 0
0 2 4 6 8 10 12 14 16
0 2 4 6 8 10 12 14 16

Wavelength ), (~m) Wavelength). (tJrn)

(b) (b)

+ . . ·rr J-t- r-\07 ~-F ~-~- -~-I

0.6 I- f--t- !

o.s

0.4

0.3

0.2

02 4 6 8 10 12 14 16 0.1 2 46 Ii
Wavelength A (pm) 0
legend 8 10 12 14 16
- =reflection 0
= transmission
Wavelength ), (prn)

legend

- "' reflection
···---- = transmi~sion

674 Infrared and Thermal Testing

semiconductors with a diamondHke (15) R I
coating it is necessary to include p
transmission energy as in Eq. 1. For
emissivity recalculation the internal (16) T
reflections have to be taken into account.
The part of the energy absorbed in every By using Eqs. 14 and 16, reflectivity p and
layer corresponds to the layer emissivity. transmissivity t can be evaluated as
functions of wavelength /,.Together with
Assuming single semitransparent layer Eqs. 1 and 2, these values can then be
as shown in Fig. 24, the total absorption A used to evaluate the emissivity for any
includes the reflection from the second dielectric material with and without tile
surface:" internal reflections. ~vfaterial thickness is
assumed to be much larger than the
(14) A (1 - p)(1 - 1) applied wavelength (Eq. 16), or wave
interference must be considered, too.
1 - p1
For multilayer semitransparent
Equation 14 was derived by a net structures with thin coatings - for
radiation technique, under the example, silicon with diamondlike
assumption of isothermal conditions coating and germanium with diamondlike
(absorption does not increase the coating~ more complex formulas are
temperature). Similarly, it is possible to used (Fig. 24):'·s
measure the reflected and transmitted
energy fractions experimentally.

FIGURE 22. Reflectivity and transmissivity for silicon in band FIGURE 23. Reflectivity and transmissivity for germanium in
from 1.4 to 2.5 ~m: (a) silicon; (b) silicon with diamondlike range from 1.4 to 2.5 11m: (a) germanium; (b) germanium
coating. with diamondlike coating.

(a) (a)

0.6

0.5

0.4

0.3 I

0.2

0.1 i_1

0 1.6 1.8 2 2.2 2.4 1.4 1.8 2 2.2 2.4
1.4 Wavelength), (!-lm)
Wavelength), (1-lm)

(b) (b)
0.7 i -.--. _: .. ,_
"l ;-- -1
0.61-- 0.71--j- JI

0.6 ~- - - - . ~-i·~ .J-.-~ ~I

0.5 -- :: i=L~ =l-1 i \

1 i :: l.~ . ·.y__rr· -- -1--l___J_'

0.4 ~ - ----·j -~

I

0.3 ' '-v.,__;-,__..::;..;_,:..•• ~-~:;:::::.. ·_j----., -,

0.2 ' --tI- t.I - I . II o.1 1 _ '--........_- ~I -+ 1
0.1 ,_ - ,
__.L +f ~: ' '-~ J _l_

0 2 2.2 -j ' 0
1.4 1.6 1.8
2.4 '1.4 1.6 1.8 2.2 2.4

Wavelength /, (l-Im) Wavelength ). (!-lm)

legend legend

-=reflection --=reflection
···-·--=transmission ....... = transmission

Infrared Thermography of Electronic Components 675

(17) T (1 - Pt}(l - rz)t. (19) II Pt + (1 - 2pt)Pzt2
(18) A - PIPzl2
1 - P1 pz-r 2
(1- p,)(l- p,t)(l-t)
where p1 and p2 arc reflectivities for both
1 - PtPzt2 layers and tis the transmissivity for the
upper layer.
FIGURE 24. Semiconductor structures for
emissivity evaluation: (a) semitransparent The results of measurements of
structure; (b) multilayer structures.
emissivity for aluminum with different
(a)
surface states are presented in Fig. 19. For
aluminum the polynomial

approximations of the emissivity are
provided over the spectral range used by

thermography, that is, 2.5 to 14 pm:

(20) <(!.)

9,3 93 where 'A :::: wavelength (pm) and E('A) is
expressed as a percentage. See Table 2.
'/ \ SHkon, n,, '"
\ !0,2 9p2 Both for the single and the multilayer
Germamum, ncu -ree structure R(J,) and T(J,) are measured as
shown in Figs. 20 to 23. The quantity for
\ Air, n~ n()..) is yielded by using Eqs. 14 and 16
and the following relation for
reflectivity p:

(21) p (11 - 113 ) 2
{H + 113 ) 2

(b) where lla is the reflective index for air;

a\)' typically lla = 1. In more predse
calculations naO•) can be provided 10 as the
cauchy or sellmeier formula:

D!amondlike TABLE 3. Radiatlon properties of semiconductors.
coating, n0 tc
Wavelength RTA p f /)
Silicon, n5,, ts,
Germanium, nee, tee (~rn)

legend Silicon 0.46 0.53 0.01 0.30 0.29 0.39 3.43
n~ = refraction index for air 2.5 to 5.5 J.Jm 0.38 0.36 0.26 0.30 0.21 0.48 3.45
nc "'" refraction index for diamond like coating 8to12J.Jm
0.54 0.46 0.00 0.37 0.37 0.26 4.10
nee = refraction index for germanium Germanium 0.54 0.45 0.01 0.37 0.37 0.26 4.14
nSJ = refraction index for silicon 2.5 to 5.5 J.lm
0, = angle of incident radiation 8to12pm
9 , = angle of reflected radiation
'~1 = transmissivity for diamond like coating R = reffQcted energy
tee = transmissivity for germanium
!~; = transmissivity for silicon T ==transmitted energy

A = absorbed energy

r = reflectivity

r =transmissivity

f' = emissivity
n =refractive index

TABlE. 2. Coefficient for polynomial approximation of emissivity for aluminum.

Test Object Co c, c, c, c, c,

Aluminum 16.87 -5.64 5.22 -1.37 0.13 -0.004
Anodized aluminum, black -31.36 54.88 -2.04 -1.65 0.22 -0.008
Anodized aluminum, not black 20.04 4.77 -2.13 0.22 --0.007
22.75 -0.007
Aluminum with coating 63.45 -1.23 -.t.63 0.19
-37.61

676 Infrared and Thermal Testing

(22) "" I + 5. 7:l87 x I 0""4 ),2 Conclusions

1? - 595260 In this chapter the measurements of the
spectral emissivity for the semiconductors
where/, is wavelength (pm). and aluminum with different surface
coatings are presented. For
In Table 3 radiation proprieties for semiconductors the emissivity is quite
silicon and germanium are presented. low, except for that of silicon in the long
wavelength range. This effect was not
Symbols U, T and A denote the fraction of observed for germanium. A thin l<1yer of
the reflected, tr<lnsmitted and absorbed diamond on the semiconductor docs not
energy. Absorbed energy property ;\ increase the emissivity very much but
corresponds to the emissivity of the works as <mlireflective coating, especially
semitransparent window if the internal in short wavelength range. For aluminum
reflection is taken into consideration . widely used in electronics, both the
However, using Eqs. 14 and 16 can help anodizing and the covering by the
find the reflectivity p, the transmissivity 1 diamond increases the emissivity
and the emissivity f for tile thick material significantly. From the measurement it b
when there are no internal reflections. possible to ide.ntify the wavelength
dependent optical parameters of
The obtained parameter values agree semitransparent materials: n, p and 1.
with the values published and measured
by other techniques~ for example, the
refraction indexes10 ,_are Htit· = 3.99 and
nsi = 3.49. For multilayer semiconductors
the total amount of energy absorbed in
whole structure is provided (fable 4).
~vfore detailed investigations need to
include the incident and reflective ·wave
interference because the diamond
thickness is of the same order as the
infrared \\'avelength.

TABlE 4. Radiation proprieties of
semiconductor multilayers.

Wavelength RT A
(pm)

Silicon with Diamondlike Coating

2.5 to 5.5 j.Jm OAO 0.54 0.06

8to12pm 0.38 0.32 0.30

Germanium with Diamondlike Coating

2.5 to 5.5 j.Jm 0.43 0.54 0.03

8 to I 2 ~m 0.50 0.44 0.06

R"' reflected energy
T"' transmitted energy
A"" absorbed energy

Infrared Thermography of Electronic Components 677

References

1. KOlzer, J., E. Oesterschulze and

G. Deboy. "Thermal Imaging and
~vfeasurement Techniques for
Electronic Materials and Devices."
Microelectrooic Engineering. Vol. 31.
Amsterdam, Netherlands: Elsevier
Science Publishers (February 1996):
p 251-270.
2. Nishino, S. and K. Ohshima. "A Study
on Fault Detection for IC Boards Using
Thermography.11 Systems and Computers
in japan. Vol. 29, No. 5. Bognar Regis,
\"'est Sussex, United Kingdom: \-\'iley
lnterScience (May 1998): p 49-61.
3. Burggraaf, P. "Imaging: Microscopy
and Thermography." SeJninnuluctor
lntemational. Vol. 9, No. 7.
Des Plaines, IL: Cahners Business
Information Uuly 1986). p 58-65
4. Siegel, R. and]. Howell. Thermal
Radiation Heat Transfer. New York, NY:
Hemisphere Publishing (1989).
5. Sala, A. Radiation Heat Tnmsf'er lin
Polish). Warsaw, Poland: WNr (1982).
6. Burakowski, T. et al. Promienniki
PodC7.{'(Wieni lin Polish]. \'\7arsaw,
Poland: WNT (1970).
7. \Viecek, B. and lvL Grecki. "Technical
Method of Emmisivity Correction in
'l'hermography." Qilll11titatil'e l11(rared
Tllcrmograp/1)' (QIRT '94) [Sorrento,
Italy, August 19941. Eurotl!erm
Seminar 42. Paris, France: Editions
EuropCenncs Techniques et Industries
(1995): p 253-259.
8. ~vfadura, H., H. Polakowski and
ll. Wiecek. ''MWlR and LWIR
Emissivity !vfeters.11 Paper B3.
Quantitative Infrared Then1wgmpl1)'
(QIRT '96) [Stuttgart, Germany,
September 1996). Eurotherm
Seminar 50. Stuttgart, Germany:
Universitat Stuttgart, lnstitut flir
Kunstoffprlifung und Kunststoffkunde.

9. \'\'iecek, ·n. and H. Madura. "Radiative

and Convective Heat Transfer in
"tvficroelectronit:s." Paper BS.
Quantitative In(rarecl Tflcn1WStafJI1)'
(QIRT '96) !Stuttgart, Germany,
September 1996j. Eurotherm
Seminar 50. Stuttgart, Germany:
Universitiit Stuttgart, Jnstitut fiir
Kunstoffprlifung und Kunststoffkunde.
10. Lide, D.L., ed.lland/Jouk o(Cimnistry
and Pllysics, 76th edition. New York,
NY: CRC Press (1995-1996).

678 Infrared and Thermal Tesflng

CHAPTER

Infrared and Thermal
Testing Glossary

Herbert Kaplan, Honeyhill Technical Company,
Norwalk, Connecticut
Jean-Claude Krapez, French National Aerospace
Research Establishment (ON ERA), Chatillon, France
Minh Phong Luong, Ecole Polytechnique, Paris, France
Xavier P.V. Maid ague, University Laval, Quebec,
Quebec, Canada
Gary L. Orlove, FUR Systems, North Billerica,
Massachusetts
Nik Rajic, Defence Science and Technology
Organisation, Melbourne, Australia
Andres E. Rozlosnik, 51 Termografia lntrarroja, Buenos
Aires, Argentina

PART 1 . Terminology

Introduction acceptance level: In contrast to rejection
le\•el, te.':.l level above or below which,
Many of the definitions in this glossary depending on the test p<lfameter, test
are adapted from the Nondestructive Testing
Handbook, second edition: Volume 10, objects are acceptable.' Compare
Nundestructil'e Testing Oren•iew. 1 These and rejection lcl'el.
other definitions in this glossary have accuracy: Degree of conformity of a
been modified to satisfy peer review and
editorial style. References given in this measurement to a standard or true
glossary should be considered not
attributions but rather acknO\\'ledgments value.'
and suggestions for further reading. adaptive thresholding: Threshold value

The definitions in this Nondestructiv£' varying with inconstant background
Testing Handbook volume should not be gray Jevel. 1
referenced for inspections performed agency: Organization selected by an
according to standards or specifications or authority to perform nondestructive
in fulfillment of contracts. Standards testing, as required by a specification
writing bodies take great pains to ensure or purchase order. 1
that their documents are definitive in
wording and technical accuracy. People algorithm: Prescribed set of well defined
working to written contracts or rules or processes for the solution of a
procedures should consult definitions mathematical problem in a finite
referenced in real standards when number of steps. 1•5
appropriate.
ambient light: Light in the environment
This glossary is provided for as opposed to illumination provided
instructional purposes. No other use is by a visual testing system. 1
intended.
ambient operating range: Hange of
A ambient temperatures over which an

absolute temperature: Temperature instrument is designed to operate
measured from absolute zero
temperature, expressed in kelvin (K) within published performance
in 51. 1 specifications.3
ambient temperature: 'Jemperature of
absolute temperature scale: Temperature
measurement scale based on coldest immediate surroundings and
possible temperature equal to 0. (See
rankine and kell•in).2 environment where a lest or
measurement takes place. A parameter
absolute zero: Temperature that is zero
on the kelvin or rankine temperature used to compensate for radiation
scales. The temperature at which no reflected from test object and air in
molecular motion takes place in a the field of view.
,TiateriaL3 ambient temperature compensation:

absorptivity (absorptancc): Proportion Correction built into an instrument to
(as a fraction of 1) of the radiant provide automatic compensation in
energy impinging on a material's
surface that is absorbed into the the measurement for variations in
material. Par a blackbody, this is unity instrument ambient temperature.3
(1.0). Technically, absorptivity is the amplitude response: That property of a
internal absorptance per unit path
length. fn thermography, the two test system whereby the amplitude of
terms have sometimes been used the detected signal is measured
interchangeably.3 without regard to phase.' ··1
analog-to-digital converter: Circuit

whose input is information in analog
form and whose output is the same
information in digital form. 1•5
anisotropy: A material's characteristic of

exhibiting different values of a

property (acoustic velocity, for
example) in different directions in the
material because of different
arrangements of atoms.1
annealing: Process of healing and cooling

a material, usually to reduce residual
stresses or to make it softer. 1

680 Infrared and Thermal Testing

anomaly: Discontinuit)'. A variation from B
normal in product quality or material
property. 1 background noise: Signals that originate
from the test object, the test
AOQ: Average outgoing quality. instrument and their surroundings
and that interfere with test signals of
AOQL: Average outgoing quality limit. interest. It may have electrical or
AQL: See acceptable quality level. mechanical origins. Sometimes called
grass or hash.1
apparent temperature: Target surface
temperature indicated by an infrared background signal: Steady or fluctuating
output signal of a test instrument
point sensor, line scanner or imager, caused by the presence of acoustic,
generally taking the emissivity into chemical, electrical or radiation
conditions to ·which the sensing
account.:~ element responds.1

arc: Luminous high temperature discharge background temperature, instrument:
Apparent ambient temperature of the
produced when an electric current scene behind and surrounding the
flows across a gap. 1 instrument, as viewed from the target.
arcing: Electric current flow through a The reflection of this background may
gap, often accompanied by intense appear in the image and affect the
temperature measurement. Most
heat and light.' quantitative thermal sensing and
arc welding: See electric arc welding. imaging instruments provide a means
artifact: In nondestructive testing, an for correcting measurements for this
reflection.3
indication that may be interpreted
erroneously as a discontinuity. 1 background temperature, target:
artificial discontinuity standard: See Apparent ambient temperature of the
acceptance standard. scene behind and surrounding the
artificial discontinuity: Reference point, instrument, as viewed from the
such as a hole, groove, implant or
instrument. \-\'hen the rov of a point
notch, that are introduced into a
sensing instrument is larger than the
reference standard to provide target, the target background
accurately reproducible sensitivity temperature will affect the instrument
levels for nondestructive test reading.3
backscattering, infrared: Reflection of
equipment. A manufactured material thermal energy - e.g., generated by
anomaly. 1 the ground and reflecting off the
ASNT: The American Society for underside of clouds or inversion
Nondestructive Testing. layers, or unwanted front surface
ASNT Recommended Practice No. SNT- reflections from a transparent optical
TC-lA: Set of guidelines for employers element.
black body: See blackbod)'.
to establish and conduct a blackbody: Hypothetical radiation source
nondestructive testing personnel that yields the maximum radiation
qualification and certification energy theoretically possible at a given
program. SNT- TC-lA was first issued in temperature. A blackbody will absorb
ail incident radiation falling on it. By
1968 by the Society for Nondestructive definition it has an emissivity of 1.0.
Testing (SNT, now ASNT) and has been See also emissivit)1• 1
revised every few years since. 1 bolometer, infrared: Thermal infrared
detector in which electrical
atmospheric temperature: Temperature conductivity changes with
of atmosphere sensed by scanner. temperature.
borcscope: Industrial mdoscope.
atmospheric windows (infrared): borescopy: Technology of the borescope
Spectral intervals ·within the infrared and its application to 11011destructiw
testing.
spectrum in which the atmosphere burning: Extreme overheating of a metal.
Makes gralns excessively large and
transmits radiant energy we1l causes the more fusible constituents of
(atmospheric absorption is a steel to melt and run into the grain
minimum). These are roughly defined boundaries or it may leave voids
as 2 to 5 ~m and 8 to 14 pm. 3 between the grains. Steel may be
attenuation: Decrease in signal oxidized to the extent that it is no
magnitude during energy transmission longer usable and cannot be corrected
from one point to another. This loss by heat treating but may he remelted. 1

may be caused by absorption,
reflection, scattering of energy or

other material characteristics or may
he caused by an electronic or optical
device sucl1 as an attenuator.1
automated system: Acting mechanism
that performs required tasks at a

determined time and in a fixed
sequence in response to certain
conditions and instructions. 1

Infrared and Thermal Testing Glossary 681

c certification: Process of providing written
testimony that an individual is
calibration: Adjusting an instrument so qualified. See also crrlifkd. 1
that its readings agree ·with a
certified: Having written testimo11y ol
standard.:~ qualification. See also certi{ication.J

calibration accuracy: Accuracy to which charge coupled device (CCD): Solid state
a calibration is performed, usually optical sensor widely used in imaging
based on the accuracy and sensitivity inspection systems for its accuracy,
of the instruments and references used high speed scanning and long service
in the calibration.-~ life. 1 Incoming radiation induces
electrical charges stored in a
calibration check: Routine check of an capacitor-like semiconductor
instrument against a reference to structures and later transferred to
ensure that the instrument has not ide'rltical neighbor structures, ready for
deviated from calibration since its last reading.
use. 3
closing: In image processing, dilation
calibration reflector: Reflector with a followed by erosion. A single pixel
known dimensioned surface closing connects a broken feature
established to provide an accurately separated by one pixel. 1 See also
reproducible reference level. 1 matllematical mU!plwlugy and opening.

calibration sourcc1 infrared: Blackbody code: Standard enacted or enforced as a
or other target of known temperature Ia--w. 1
and effective emissivity used as a
calibration referencc.3 coefficient of thermal expansion: Linear
expansion or contraction per unit
candela: Base unit of measure in SI for length per degree of temperature
measuring luminous intensity. The change between specified lower and
luminous intensity in a given upper tempewture limits. 1
direction of a source that emits
coefficients of the filter: Values in a
monochromatic radiation of frequency mask that serves as a filter in image
540 x 1012 Hz and that has a radiant processing. 1
intensity in that direction of
1.4641 m\·V·sr1• Symbolized cd. color: Aspect of visible light sometimes
Formerly known as candle. 1 used to identify wavelength or spectral
candle: Former name for candela. I band, as in ht'u-culor mdiometry
capacitance, thermal: Amount of heat (meaning a method that measures in
that an object can store. The term two spectral bands); also used
thermal capacitance is used to describe conventionally (visual color) as a
heat capacity in terms of an electrical means of displaying a thermal image,
analogy, where loss of heat is as in color thermogram.3
analogous to loss of charge on a
capacitor. Structures with high thermal colored body: See nunsmybody.
capacitance change temperature more complete testing: Testing of an entire
slowly than those with low thermal
capacitance.3 production lot in a prescribed manner.
capacity, heat: Ability of a material or Sometimes complete testing entails
structure to store heat. The product of the inspection of only the critical
the specific heat and the density of regions of a part. One hundred
the material. This means that denser percent testing requires the inspection
materials generally will have higher of the entire part by prescribed
heat capacities than porous materials.J methods. Compare smnpli11g, partiaJ.l
Heat capacity is the amount of energy conduction: Heat transfer occurring when
more energetic particles collide with
O·m-3-K-1) required to elevate by one -and thus impart some of their heat
energy to- adjacent less energetic
degree a given volume of material. (slower moving) particles. This action
Among common materials, 'i\'ater has is passed on from one atom (or free
one of the highest heat capacities; air, electron) to the next in the direction
one of the lowest. of cooler regions. Thus, heat always
casting: Object of shape obtained by flows from a warmer to a cooler
solidification of a substance in a mold. region. 1
CCD: See charge coupled device. conductivity, thermal (k): Material
celsius (centigrade): Temperature scale property defining the relative
capability to carry heat by conduction
based on 273 K (0 oc ~ +32 °F) as the in a static temperature gradient.
Conductivity varies slightly with
freezing point of ·water and 373 K temperature in solids and liquids and
with temperature and pressure in
(100 oc ~ 212 °F) as the boiling point gases. It is high for metals (copper has
a k of 380 \V-nr1·K-1) and low fo1
of water at standard atmospheric gases and porous materials (concrete
pressure. A relative scale related to the has a k of 1.0 \·V·m-l.K-1).:~

kelvin scale (0 oc = 273.12 K;

1 °C ~ 1 K)-'

682 Infrared and Thermal Testing

continuous annealing furnace: Furnace crack: (1) A break, fissure or rupture,
in which castings are heat treated, by usually V shaped and relatively narrow
and deep. A discontinuity that has a
being passed through different heat relatively large cross section in one
zones kept at constant temperatures. I direction and a small or negligible
cross section when viewed in a
continuous casting: Casting technique in direction perpendicular to the first. 1
which an ingot, billet, tube or other (2) Propagating discontinuities caused
shape is continuously solidified while by stresses such as heat treating or
being poured so that its length is not grinding. Difficult to detect unaided
because of fineness of line and pattern
determined by mold dimensions.I (may have a radial or latticed
contrast: Difference in visibility appearance). 1

(brightness, color or temperature) crater: (1) In machining, a depression in
the cutting tool face eroded by chip
between an indication and the cont<JCt. (2) In arc or gas fusion
surrounding surface.1 welding, a cavity in the weld bead
surface, typically occurring when the
convection: Type of heat transfer that heat source is removed and
takes place in a moving medium and insufficient fil1er metal is available to
fill the cavity. 1
is almost always associated with
transfer between a solid (surface) and a C-scan: Data presentation technique
applied to reflection and transmission
moving fluid (such as air), whereby techniques. It yields a
two-dimensional plan view of the
energy is transferred from higher object but no depth indications unless
temperature sites to lower temperature special gating procedures arc used. 1
sites. 3
cooling stresses: Residual stresses cutoff frequency: Upper or lower
resulting from nonuniform frequency corresponding to the
spectral response of a filter or
distribution of temperature during amplifier, at a specified amount less
cooling. 1 (usually 3 dB power or 6 dB
corrosion: Deterioration of a metal by voltage/amplitude) than the
chemical or electrochemical reaction maximum response.1

with its environment. Removal of D
material by chemical attack, such as
D* (detcctivity star): Detectivity
the rusting of automobile expressed inversely so that higher D*s
components. 1 indicate better performance.
crack, cold: Cracks that occur in a casting Sensitivity figure of merit of an
infrared detector. })* is taken at
after solidification, due to excessive specific test conditions or chopping
frequency and information bandwidth
stress generally resulting from and displayed as a function of spectral
nonuniform cooling.1 wavelength. 3 D* is the detectivity
crack, cooling: Cracks in bars of alloy or scaled to the unit sensitive detection
area, with detectivity corresponding to
tool steels resulting from uneven the inverse of the nobe equivalent
flow.
cooling after heating or hot rolling.
They are usually deep and He in a defect: Discontinuity ·whose sin·, shape,
orientation or location make it
longitudinal direction, but are usually detrimental to the useful servke nf its
not straight.1 host object or which exceeds an
crack, grinding: Thermal cracks caused accept/reject criterion of an applicable
specification.1 Note that some
by local overheating of the surface discontinuities may not affect
being ground.1 :-.erviceability and are therefore not
crack, hot: Cracks that develop before the defects. 1 Compare dismntinuity and
i11dicatiou. 1
casting has completely cooled, as
contrasted with cold cracks, that deformation: Change of '>hape under
develop after solidification. 1 Also load. 1 See aho creep and elastic
called Jwt fear. de(umwlion.

crack, transverse: Cracks at right angles delamination: l_aminJI disc011linuity,
to the length of the test ohject. 1 gener<~lly an area of unbund('d Jay('r;:;
of matnial.\. 1
crack, weld: Cracks in weld fusion zones
or adjacent base metal. Usually a result
of thermal expansion or contraction
stresses related to temperature changes
during welding. I

Infrared and Thermal Testing Glossary 683

depth of field: In photography or discontinuity, artificial: Reference
thermography, the range of distance discontinuities such as holes,
indentations, cracks, grooves or
over which an imaging system gives notches that are introduced into a
satisfactory definition when its lens is reference standard to provide
accurately reproducible indications for
in the best focus for a specific determining sensitivity levels. 1
distance. 1
depth of fusion: Depth to which the base discontinuity, primary processing: In
metal melted during welding.l metals processing, a material anomaly
produced from the hot or cold
detector, infrared: Transducer element working of an ingot into forgings, rod
that converts incoming infrared and bar. 1

radiant energy impinging on its discontinuity, service induced: I\•laterial
anomaly caused by the intended use
sensitive surface to a usehli electrical of the part.'
signal. 3
diffuse reflector: Surface that reflects a display resolution, thermal: Precision
portion of the incident radiation in with which an instrument displays its
assigned measurement parameter
such a manner that the reflected (temperature), usually expressed_ in
degrees, tenths of degrees, hundredths
radiation is equal in all directions. A of degrees and so forth.J
mirror is not a diffuse reflector.::~
diffusion, heat: See thermal diffusion. dissipation: Generation of heat by plastic
diffusion, mass: Process by which deformation.

molecules intermingle as a result of distal: In a manipulative or interrogating
concentration gradients or thermal system, of or pertaining to the end
motion. 1 Spreading of a gas through opposite from the eyepiece and
other gases "\Vithin a volume. farthest from the person using the
system. Objective; tip. 1
diffusivity, thermal: See thermal
dif{usivity. E

dilation: In image processing, the effective emissivity (e*): Measured
condition of a binary image where the emissivity value of a particular surface
pixel in the output image is a 1 if any under existing measurement
of its eight closest neighbors is a 1 in conditions (rather than the generic
tabulated value for the surface
the input image. See also closing, material) that can be used to correct a
erosion, mathematical morphology and specific measuring instrument to
opeHing. 1 provide a correct temperature
directional properties, material: measurement.3

Properties whose magnitudes depend cffusivity, thermal: Ability of heat to
on the relation of the test axis to the escape from a body, expressed as a
characteristic of that body.~ Square
specific direction in the metal, root of the product of thermal
resulting from preferred orientation or conductivity, mass density and specific
heat.
from fibering in the structure. See
anisolropy. 1 elasticity: Ability of a material to resume
directional properties, radiation: its former shape after deformation. 1
Radiation properties (emissivity,
electric arc \\'elding: Joining of metals by
absorptivity, reflectivity) as referenced heating with electric arc. Also called
to a particular direction. See also arc weldi11g. 1
llemispllerical properties, radiatio11. 1
direct viewing: Viewing of a test object in electromagnetic interference: Sec
EMI!RFI noise.
the viewer's immediate presence. The
EMI/RFI noise: Disturbances to electrical
term direct viewing is used in the fields signals caused by electromagnetic
of robotics and surveillance to interference (EtvH) or radio frequency
interference {RFI). In thermography,
distinguish conventional from remote this may cause noise patterns to
viewing. 1 appear on the display:{

discernible image: Image capable of
being recognized by sight without the
aid of magnification. I

discontinuity: Intentional or

unintentional interruption in the
physical structure or configuration of a
part.IA After nondestructive testing,

unintentional discontinuities

interpreted as detrimental in the host
object may be called flaws or de{ect~.

Compare defiYl, dislocalion and
indication. 1

684 Infrared and Thermal Testing

emissivity: Variable ratio of the total external discontinuities: Discontinuities
energy radiated by a given surface at a on the outside or exposed surface of a
test object. 1
given temperature to the total energy
radiated by a blackbody at the same F
temperature. Emissivity can be total,
directional or hemispherical. EmissivHy fahrenheit: Temperature scale based on
is a surface phenomenon depending 32 oF as the freezing point of water
on surface condition and composition. and 212 °F as the boiling point of
water at standard atmospheric
Smooth materials have lower pressurei a relative scale related to the
emissivities than rough or corroded rankine scale 10 oF= 459.67 R; 1 °F
materials. 1 Emissivity values range (DT) ~ 1 R (DT)] 3
between 0 for a perfect reflector to 1.0
false indication: Test indication that
for a blackbody. could be interpreted as originating
from a discon.tinuity but which
endoscope: Device for vle\ving the actually originates ·where no
interior of objects. From the Greek discontinuity exists. 1 Distinct from
vwrds for inside view, the term nonrelevant indication.1 Compare
endoscope is used mainly for medical de(ect. 1
instruments. Nearly every medical
endoscope has an integral light source; feature extraction: From an enhanced
image, derivation of some feature
many incorporate surgical tweezers or values, usually parameters for
other devices. Compare borescope. 1 distinguishing objects in the image. I
environmental rating: Rating given an
operating unit (typically an electrical fiber optic, infrared: Flexible fiber made
of a material that transmits infrared
or mechanical enclosure) to indicate energy, used for making noncontact
the limits of the environmental temperature measurements when
there is not a direct line of sight
conditions under which the unit will between the instrument and the
function reliably and within published target.3
performance specifications.3
fiber optics: Technology of light
erosion: (1) Loss of material or transmission through fibers such as
degradation of surface quality through plastic, glass or quartz.I

friction or abrasion from moving field: In video teclmology, one of two
fluids, made worse by solid particles ln video picture components that
together make <J frame. Each picture is
those fluids or by cavitation in the divided into two parts called fields
moving fluid. (2) In image processing, because a frame at the rate of thirty
frames per secoi1d in a standard video
condition of a binary image where the output would otherwise produce a
pixel in the output image is a 1 if each flicker discernible to the eye. Each
field contains one half of the total
of its eight neighbors is a 1 in the picture elements. Two fields are
input image. See also closing, dilation, required to produce one complete
mathematical morphology and openins. 1 visible light picture or frame so the
eutectic liquid: Liquid having a field frequency is sixty fields per
proportion of metals such that two or second and the frame frequency is
thirty frames per second. 1 In infrared
more solid phases form at the same technology there can be four fields.

temperature during coo1ing.l field of vie·w: Range or area where things
eutectic point: Temperature and can be seen through an imaging
system, lens or aperture.1 Angular
proportion of metals· at which two or subtcnse (expressed in angular degrees
or radians per side if rectangular, and
more phases of a eutectic liquid form. angular degrees or radians if circular)
Compare eutectoid. 1 over which an instrument wiJl
eutectoid: Similar to eutectic but in a integrate all incoming radiant energy.
solid system during cooling. 1 In a radiation thermometer, the field of
evaluation: Process of determining the l'iew is the target spot size; in a
scanner or imager the field ofview is
magnitude and significance of a the scan angle or picture size or total
discontinuity after the indication has field of view (TI;OV).3 Compare depth
o f field.
been interpreted as relevant.
Evaluation determines if the test

object should be rejected, repaired or
accepted. See indication and
inteJpretati011. 1
examination: Process of testing materials,

interpreting and evaluating test
indications to determine if the test
object meets specified acceptance
criteria. 1
exfoliation: Corrosion that progresses

approximately parallel to the outer
surface of the metal, causing layers of
the metal to be elevated by the
formation of corrosion product. 1
exitance, radiant: See mdiosity.

Infrared and Thermal Testing Glossary 685