The Skip of a Stone ... James Keay | 20370096 | IDA III | 4C - ABEE3007 | 3540
CONTENTS Tectonic Response | Preliminary Design Intent FragMENted Layers ........................................................................................................................................ 3 Innovative Solution ........................................................................................................................................ 4 Material and Enviroment The Nutrient Management Plan (NMP) ........................................................................................................ 5 Raw Sewage .................................................................................................................................................... 6 A short-term response................................................................................................................................... 7 Phosphorus-binding compounds or beneficial microbes designed to slowly dissolve ................................. 8 Role of clay minerals in controlling phosphorus............................................................................................ 9 Types of Phosphorus ...................................................................................................................................... 9 Optimal Clay Material .................................................................................................................................... 9 Scientists Perfected the Skipping Stone ....................................................................................................... 10 Moving forward - Concluding thoughts........................................................................................................ 12 Testing Testing stones – personal journey ............................................................................................................... 13 Finding the perfect stone ............................................................................................................................. 15 Creating a Plastic Mould for Accurate and Repeatable Testing .................................................................. 16 Testing the Effects of Phosphorus-Binding Compounds on Phosphorus Levels in the River Avon ............ 20 Testing the Effects of Calcium on Phosphorus Reduction in the River Avon ............................................... 21 Testing the Effects of Iron on Phosphorus Reduction in the River Avon ..................................................... 22 Effects of Clay................................................................................................................................................ 23 Workmanship Creating the Final Stone Design ................................................................................................................... 25 Creating the Second Mould Half ................................................................................................................. 26 Testing the Final Mould ................................................................................................................................ 28 Creating the Desired Material ...................................................................................................................... 29 Testing the final Stone - My Result ............................................................................................................... 31 Reflection ...................................................................................................................................................... 32 Bibliography ................................................................................................................................................. 33 2
In line with my current studio project ‘Fragmented Layers,’ which is an archaeological hub situated in Bath Quays Waterside adjacent to the River Avon, this project aims to explore two pressing challenges impacting Bath: the silent pandemic eroding men’s mental health alongside dwindling biodiversity destabilizing our interconnected ecosystems. Suicide claims more UK men under 45 than any other cause, with over 4,179 deaths by suicide yearly (CALM, 2023). 74.1% of all suicides are male (Lauren Revie, 2023). Research links these outcomes to isolation and barriers to support seeking driven by stigma. Facilitating inclusive spaces for males to gather, communicate and bond without judgement is vital to combatting this silent epidemic eroding men’s mental health. Additionally, Scientists estimate humans could destroy 30% of Earth’s species in decades (IPBES, 2019) — outpacing historical norms 1,000-fold (IPCC/SEI). Locally, a 2010 Bath/NorthEast Somerset assessment found 27% of regional species — 308 plants and animals—under threat. Fewer species directly erodes essential ecosystems communities depend upon for sustainability. Interconnectedness falters as biodiversity vanishes, risking collapse of nature’s lifesupport systems. Yet conservation efforts protecting remaining diversity strengthen ecological foundations and help mitigate risks. FragMENted Layers 3
So how can one innovative solution bridge these two critical yet vastly different challenged to Baths sustainable mental, societal and ecological health? In this project, I will subtly integrate the collective activity of ‘skipping stones’ into my archaeological hub design. This concept involves throwing flat, ovular rocks across a relatively calm water surface in order to tally the highest number of skips before inevitable sinking. Having grown up competing with friends to achieve the longest stone skip counts, I intimately understand the enjoyable and bonding nature of this traditional masculine pastime. The inclusion aims to foster a cooperative yet competitive atmosphere for males across generations to connect through shared nostalgia and friendly rivalry. Although this concept aims to address aspects of male mental health, it does little to tackle biodiversity challenges, especially along Bath’s waterside which borders the river Avon. Spanning 60 miles from Bath downstream to the Bristol Channel, the Avon is fringed by rich riparian plant life and habitats for threatened animal and plant species. However, this vibrant ecosystem is declining. Understanding what the river requires to combat eutrophication and support biodiversity in the buffers surrounding it, targeted deposition of necessary ‘Vitamins, minerals or elements’ into the river can help combat this growing threat. While striking an ecological balance to prevent negatively impacting oxygen levels, this strategy fuels aquatic plant photosynthesis, feeds aquatic food chains and boosts growth in riparian vegetation - all while keeping the river ecosystem alive. Creating skipping stones from essential components which, upon impact with the river, begin to slowly break down and dissolve can provide the targeted deposition the river’s ecology so desperately needs. A skipping stone used to heal a man’s mental health will also save countless species with as little as a throw... Innovative Solution 4
The Nutrient Management Plan helps reduce phosphorus levels in the River Avon Special Area of Conservation (SAC) to comply with EU conservation directives (Caroline Chapman, 2015). It ensures development does not increase phosphorus loading that would conflict with conservation objectives. Bristol University and the British Geological Society are examining phosphorus contributions from Avon geology, like the Upper Greensand geology within the upper reaches of the Avon, Nadder, and middle reaches of the Wylye. Much nutrient pollution comes from atmospheric deposition on urban/nonagricultural land. Government action on emissions reductions will help ease this in future (Giles Bryan, 2021). Urban reductions can also occur by fixing misconnected soaking drainage and implementing Sustainable Urban Drainage Systems to curb runoff of nutrients. In summary, the plan coordinates different reduction strategies across sources to manage phosphorus loading in the Avon SAC. This meets international obligations to maintain ecological standards for this protected chalk stream habitat. Achieving this numeric phosphorus standard is necessary for the River Avon’s impacted, chalk river typology. Currently, phosphorus levels across much of the catchment exceed targets and prevent conservation objectives from being achieved. Significant reductions in nutrient loading are critical to approach and attain ecological water quality standards. The Nutrient Management Plan (NMP) 5
This diagram depicts potential sources contributing to elevated phosphorus levels along the River Avon from Bath Quays to the river’s outlet. Phosphorus is an important nutrient, but in excess can cause algal blooms and eutrophication. As the Avon flows through areas of agriculture and populated cities like Bath and Bristol, effluent from sewage treatment and fertilizer runoff enter the river (Raw sewage in our rivers, 2023). Figure 1 - Raw Sewage in the River Avon Raw Sewage 6
As evidenced in numerous reports, the high level of phosphorus within the river Avon poses dire ecological challenges surrounding the river. The existing phosphorus enrichment is substantially higher than the defined standard of 50 micrograms/litre set for impacted lowland, alkaline, chalky rivers like the Avon. This threshold should be met in order to restore the ecological health of the River (European Site Conservation Objectives, 2019). The Environment Agency (EA) and Natural England (NE) monitor phosphorus levels in the River Avon SAC. Concentrations are around 100 micrograms/litre in the headwaters, declining to 65 micrograms/litre downstream (Moore, 2023). Addressing phosphorus pollution in the River Avon is a large, meticulous challenge requiring government and widespread change. While unable to permanently prevent this ongoing issue, the careful deposition of phosphorusbinding compounds or beneficial microbes could theoretically aid shortterm phosphorus removal from the water column. This could support the river’s biodiversity until more permanent measures are enforced and further researched. While not a complete solution, this creative idea is worth exploring to protect sensitive ecology from further harm. It could buy time until more comprehensive policies and scientific solutions are enacted to prevent excessive nutrient pollution long-term. A short-term response 7
Understanding how specific compounds influence and bind with phosphorus is essential to creating this short-term response. For example, iron, aluminium, and calcium compounds tend to strongly bind phosphorus into insoluble minerals, thereby reducing dissolved and bioavailable phosphorus in the river Avon (Andersen et al., 2016). Organic matter also binds some phosphorus, though this tends to be weakly bound and can be released under certain conditions. Clays and carbonates interact with and influence phosphorus also. In effect, these phosphorus-binding compounds act to strip phosphorus out of transport pathways into the river, sequestering and storing it in the surrounding landscape. This reduces phosphorus fluxes into the river. However, the content also notes that these compounds and bound phosphorus can later be released under shifting conditions like floods or water table fluctuations. This again explains the unreliability of this method for the long-term viability. Phosphorus-binding compounds or beneficial microbes designed to slowly dissolve 8
Role of clay minerals in controlling phosphorus Types of Phosphorus Optimal Clay Material Clay minerals play a crucial role in controlling phosphorus (P) availability in rivers, which are common in agricultural settings. Despite the prevalent focus on iron/ Calcium (hydr)oxides as primary agents for phosphorus adsorption, recent studies underscore the significance of clay minerals in this process (Antelo et al., 2021). Different forms of organic phosphorus (OP) compounds bind to soil minerals differently. OP includes compounds like myo-inositol hexakisphosphate (myo-IHP), glycerophosphate (GLY), and glucose-6-phosphate (G6P). Myo-IHP has 6 phosphate groups, so it has a higher adsorption capacity compared to orthophosphate monoesters like G6P and GLY, due to its higher charge density. It sticks strongly to soil minerals. But G6P is a smaller molecule, so it can bind more densely and quickly to soil, due to its lower molar mass, which enhances its adsorption density and rate (Barrow et al., 2022). In terms of soil minerals, clay minerals like kaolinite and montmorillonite are significant players in phosphorus adsorption. While goethite and gibbsite, representative of iron and aluminum oxides respectively, are also crucial, they have been studied more extensively. Clay minerals exhibit varying capacities for adsorption and desorption of OP compounds, and their selection for phosphorus management strategies should consider their chemical properties In the context of reducing phosphorus in a water body like the River Avon, the selection of clay minerals would be crucial. Considering the emphasis on myo-IHP and its strong adsorption capacity, clay minerals effective at adsorbing myo-IHP would be preferred. Kaolinite, with its ability to form complexes with myo-IHP, could be particularly suitable for reducing phosphorus levels in water bodies, especially from urban sewage (Carbinatti, 2021). Additionally, montmorillonite, known for its high surface area and cation exchange capacity, may also be effective in adsorbing OP compounds and reducing phosphorus runof 9
Diagram : (Figure 2) Experiments show that an elastic sphere with a low shear modulus (G) deforms extensively when impacting water, while a rigid sphere with a high G does not. Although both spheres have very similar radius (R), density (ρs), impact speed (Uo), and angle (βo), after 25 ms the elastic sphere rides along the air-water interface while the rigid sphere plunges below the surface. This demonstrates that the elastic sphere experiences a much greater upward force from the water. Its extreme deformability enables superior skipping ability. When the rigid sphere impacts the water surface at an angle, images show it carving an air cavity into the water as it dives below the surface (scale bar 40 mm). The rigid sphere dives beneath the surface, while the elastic sphere skips off of it. The art and science of skipping stones has been studied for centuries. Researchers have investigated how to optimize the shape, size, and material properties to achieve the most skips (Belden et al., 2016). Traditional rigid skipping stones, like flat rocks, rely on having an optimal attack angle upon impact to generate enough lift force to skip. By monitoring the collision of a spinning disc with water, scientists have discovered that an angle of about 20° between the stone and the water’s surface is optimal with respect to the throwing conditions and yields the maximum possible number of bounces. (Christophe Clanet, 2004) However, the testing shows that elastic spheres demonstrate superior skipping ability compared to rigid stones. (Figure 2) Elastic spheres easily deform on impact, increasing the wetted surface area. This larger area creates more lift force to skip at higher angles. Also, vibrations in elastic spheres interact with the water surface in ways that further augment skipping, meaning elastic spheres can skip at impact angles nearly three times higher than predicted for rigid stones before sinking. A positive feature when considering the use class for this activity will be beginner to moderate. These qualities enable elastic spheres to achieve longer, sustained skipping trajectories over multiple successive skips. In summary, elastic spheres have advantageous qualities over rigid stones that greatly improve skipping performance. Their extreme deformability facilitates higher lift forces and more efficient rebounds that together enable remarkable and robust multi-skip trajectories. Scientists Perfected the Skipping Stone 10
Figure 2 - A rigid sphere and an elastic/compliant sphere (b) In contrast, an elastic/compliant sphere with these properties: • Initial velocity = 22.0 m/s • Initial angle = 32.0° • Shear modulus (low, so it's very compliant/elastic) = 12.3 kPa • Radius = 26.2 mm • Density ratio = 0.937 (a) A rigid sphere with the following properties: • Initial impact velocity (Uo) = 24.3 m/s • Initial impact angle (βo) = 29.6° • Shear modulus (G, a measure of rigidity) = 5.66 × 105 kPa • Radius (R) = 25.8 mm • Density ratio (ρ*) = ratio of sphere density to water density = 0.959 3
Identifying a material that can function as a biodegradable carrier for delivering desired nutrients/ chemicals into the River Avon while exhibiting elastic deformability for optimal skipping presents a challenge. Balancing these different properties is essential. Releasing nutrients into the river requires a durable material capable of containing chemicals during transit, but not indefinitely. Conversely, effective skipping stones necessitate elastic deformability to prolong life through successive impacts. The ideal material must facilitate controlled breakdown to fulfill its chemical transport function while retaining elastic qualities to improve surface interactions like skipping. Furthermore, understanding the selected phosphorus-binding compound’s reaction with the material and phosphorus solution is crucial for determining the final form and safe quantity. Reconciling these competing needs complicates material selection. To address this, accurate testing and outsourcing expertise will be necessary to comprehend the requirements for creating an optimal skipping stone solution. Moving forward - Concluding thoughts 12
Testing stones – personal journey To begin my research into the sport of skipping stones, I first found it important to test out an array of stones across a relatively flat-water surface to find the most optimal stone to drive the rest of my project’s discovery. I tested 6 different stones, each with contrasting weight, shape, size, elasticity and formation (type of rock). 1 2 3 4 5 6 Rock Type Sandstone Sandstone Shale Limestone Sandstone Sandstone Size/Dimensions 5cm - 3cm 4cm - 3cm 1.5cm - 2cm 6cm - 4cm 3cm - 2cm 3cm - 2cm Shape Sphericity While mostly smooth and rounded, one side contains a large, pronounced protrusion that stretches the outline vertically and interferes with the overall spherical form. On the adjacent side, a smaller protrusion is present as well, though less prominent. Despite these obtrusions on two sides, the topside and underside of the pebble retain a rounded contour indicative of significant transport and erosion over time prior to deposition. The rock has a smooth, flat profile with an oval base, giving it the appearance of a rounded disk. The maximum thickness in the center is 15mm, tapering to thin edges around the periphery. When viewed from above, the top face is mostly circular with a diameter of 45mm, retaining a symmetrical rounded form apart from one small protrusion on one side. The protrusion slightly obscures the circularity but does not significantly distort the overall shape regularity. The bottom of the rock is oval rather than circular like the top. The stone has an irregular, asymmetric shape with no clearly defined edges or faces. Uneven protrusions give it a knobby texture with no flat sides. The thickness across the stone varies between 5-10mm, with an average thickness around 8mm. Despite the overall irregular form, the top and bottom surfaces are relatively flat. The uneven knobs and protrusions along its sides give rise to many sharp edges and points rather than smooth contours. A few small pits are scattered across the surfaces as well. The stone has a highly uneven, irregular shape, with no symmetrical form or clearly defined faces. The thickness across the rock ranges from 1.5-2.5cm, uneven due to the random protrusions and indented features across its body. The edges are all sharp and angular, as typical for an irregularly shaped rock of this type. The surfaces contain scattered small pits and dents of varying depth and width, distributed randomly across both flat faces rather than clustered in any area. Along with the pits and dents, several minor protrusions emerge to further obscure any smooth surfaces, creating a knobby profile. The rock has a smooth, flat profile with an oval base, giving it an overall appearance of a small rounded disk. The maximum thickness in the center is under 1cm, tapering to very thin edges around the oval periphery. Both the top and bottom faces are flattened with only subtle contours across the surfaces. When viewed from above, the top face is nearly circular. The small, thin, flattened structure gives it a compact hydrodynamic form. "The rock has a very smooth, well-rounded form, shaped like a vertically stretched ellipse. The top and bottom are both evenly rounded, showing a high degree of symmetry about the vertical axis and mirroring each other in contour. When viewed from the side, the elongated elliptical silhouette is evident. The edges gracefully taper to create a continuous oval outline without any sharp transitions or flat spots. Both the bird's eye view facing either the top or bottom face, and the side view facing the edges, showcase the consistent spherical contours across all aspects of the rock. Surface Texture Smooth, No cracks, breaks, or impurities are present, and the sample remains intact. smooth, No cracks, breaks, or impurities are present, and the sample remains intact. Highly irregular sharp texture with pits scattered, No cracks or breaks are present, and the sample remains intact. Highly irregular sharp texture with pits scattered, No cracks or breaks are present, and the sample remains intact. smooth, No cracks, breaks, or impurities are present, and the sample remains intact. Smooth, No cracks, breaks, or impurities are present, and the sample remains intact. Impact velocity Typical Average of 30-40 Mph Typical Average of 30-40 Mph Typical Average of 30-40 Mph Typical Average of 30-40 Mph Typical Average of 30-40 Mph Typical Average of 30-40 Mph Impact Angle Below 13° Below 13° Below 13° Below 13° Below 13° Below 13° Number of Skips 1 5 3 2 6 6 Water flow speed Regular Regular Regular Regular Regular Regular 13
Overall, the majority of my study’s showed that ovular based, medium weighted relatively flat dense rocks appeared to skip the most across the lake Each test was tested on the same day, same location and minimal time difference at Wollaton Park Lake in Nottingham. Weather was rainy with light winds although regular steady water rates across the site. Finding the perfect stone 15
I decided to create a plastic mould for my project because plastic is durable enough for repeated testing and can produce smooth, highly detailed, and accurate castings. Unlike plaster or concrete, plastic also does not react with the oxide components (iron, calcium, etc.) I plan to test. This decision was based on extensive research and multiple discussions regarding the optimal mould material. I initially attempted sand casting to produce the desired mould shape. However, the molten plastic struggled to properly wrap around and bind with the test rock sample. There were also issues with sand getting into the vacuum seal of the plastic forming machine, which could damage the equipment. Out of respect for the equipment and the validity of my test mould, I opted to use an alternative mould creation method. Creating a Plastic Mould for Accurate and Repeatable Testing 16
Using the vacuum form machine without a sand cast mould seemed to create a more accurate and precise mould around my stone sample. I cast each side of the stone in plastic then formed a cap by hand-cutting the plastic with a scalpel and sanding it to create the top part of the two-piece mould. This enabled me to pack a practice clay material into the mould and conduct an initial test. I found that applying a thin layer of non-stick liquid to the mould interior prior to packing in the clay allowed the material to more easily retain its moulded shape when removing it. There was also a surrounding line evident after mould removal which required sanding. 17
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2. 5ml per 100 L to Increase Phosphorus by 0.1Mg/L. To achieve 0.1Mg/L, Add 0.4ml into 8L stable container. 1. Stable container able to hold 8L of Distilled water. 3. Collect a 5ml sample of Phosphate solution. 4. Add 5 drops of Phosphate Reagent and wait 5 minutes. Observe change in watercolour. 5. Test above shows Distilled water (1), Phosphate water (0.1Mg/L)(2) and Phosphate water (0.2Mg/L)(3). The yellower the solution, the higher the concentration of phosphate. Microbe-Lift Plants P AquaCare Master Test Kit As we know, the existing phosphorus levels in the River Avon are substantially higher than the defined standard of 50 micrograms per litre (European Site Conservation Objectives, 2019). These standards were recently revised based on new scientific evidence regarding the impacts of phosphorus on river ecology. The revised standards are more stringent, allowing lower phosphorus concentrations (Bryan, 2015). Previously, phosphorus concentrations in the River Avon were estimated at around 100 micrograms/litre in the headwaters, declining to 65 micrograms/litre downstream (Moore, 2023). For this exploration, I will test the effects of iron, calcium, kaolinite clay, and montmorillonite clay on reducing phosphorus levels in a concentrated aqueous solution mimicking phosphorus concentration of 100 micrograms/litre in the River Avon. This will inform which type of clay and phosphorus-binding compound works best to reduce phosphorus levels to the desired standard of 50 micrograms per litre. I have chosen to test the effects at 100 micrograms/ litre because this is the highest estimated level of phosphorus in the Avon. Testing the system’s ability to handle these extreme concentrations will ensure it can also handle lower phosphorus outliers. This is the most reliable methodology. I had requested River data samples from Bristol University and the British Geological Society, but the information was not received in time. Therefore, I made the decision to create a 100 microgram/litre phosphorus solution for testing. Testing the Effects of PhosphorusBinding Compounds on Phosphorus Levels in the River Avon 1. 2. 3. 20
Testing the Effects of Calcium on Phosphorus Reduction in the River Avon I tested calcium's ability to reduce phosphorus levels in an aqueous solution mimicking the River Avon's phosphorus concentration of 0.1 mg/L (100 micrograms/ litre). Three different calcium quantities were tested: 0.05 mg/L, 0.1 mg/L, and 0.15 mg/L to evaluate phosphorus reduction across a range of calcium concentrations. Theoretically, the chemical reaction between calcium and phosphate ions (3Ca^2+ + 2PO4^3- → Ca3(PO4)2) requires 3 calcium ions for every 2 phosphate ions to form an insoluble calcium phosphate compound. This balanced equation indicates 0.15 mg/L (150 micrograms/litre) of calcium should remove 0.1 mg/L of phosphate in an ideal reaction. Using an ‘AquaCare Master Test Kit’, I observed a decline in detectable phosphate levels as calcium concentrations increased. At 0.15 mg/L calcium, the test solution appeared completely clear, consistent with full phosphate removal based on the expected theoretical data. No harmful byproducts were created during the iron-phosphate reaction, ensuring safety for potential application in the River Avon. 1. Distilled Water 2. Phosphorus concentration of 0.1 mg/L 3. 0.05 mg/L Calcium 4. 0.1 mg/L Calcium 5. 0.15 mg/L Calcium 1. 2. 3. 4. 5. 21
Testing the Effects of Iron on Phosphorus Levels in the River Avon I tested iron’s ability to reduce a 0.1 mg/L (100 micrograms/litre) phosphorus concentration by evaluating three different iron quantities: 0.05 mg/L, 0.1 mg/L, and 0.15 mg/L. Theoretically, removing all phosphorus (0.1 mg/L) from the solution using iron requires adding 180 micrograms/litre of iron(III) ions based on the reaction: Fe3+ + PO43- → FePO4(s). Using an AquaCare Master Test Kit, I observed only a slight decline in detectable phosphate levels as iron concentrations increased. Even at 0.15 mg/L iron, the solution still contained phosphorus, indicating iron is less effective than calcium for phosphorus reduction under these conditions. No harmful by-products were created during the iron-phosphate reaction, ensuring safety for potential application in the River Avon. • The reaction between iron(III) and phosphate ions is: Fe3+ PO43- → FePO4(s) • In this reaction, 1 mole of Fe3+ reacts with 1 mole of PO43- Given: • Phosphorus concentration = 0.1 mg/L = 100 μg/L • Molar mass of phosphorus = 30.97 g/mol • Molar concentration of phosphate ions: • Moles of PO43- per litre = (100 × 10-6 g/L) / (30.97 g/mol) = 3.23 × 10-6 mol/L • Since the reaction requires a 1:1 molar ratio of Fe3+ to PO43-: • Needed molar concentration of Fe3+ = 3.23 ×10-6 mol/L • Using the molar mass of iron (55.85 g/mol)Required iron concentration = (3.23 × 10-6 mol/L) × (55.85 g/mol) = 1.80 × 10-4 g/L = 180 μg/L 1. 2. 3. 4. 5. 1. Distilled Water 2. Phosphorus concentration of 0.1 mg/L 3. 0.05 mg/L Iron 4. 0.1 mg/L Iron 5. 0.15 mg/L Iron 22
Effects of Clay 23
1. 2. 3. 4. Effects of Clay 1. Distilled Water 2. Phosphorus 0.1 mg/L 3. kaolinite clay 4. montmorillonite clay kaolinite Montmorillonite I tested the effects of kaolinite and montmorillonite clays on a 0.1 mg/L phosphate water solution over two days, observing their dissolvability, reaction with the solution, and influence on phosphorus levels. Montmorillonite clay broke down faster due to its higher surface area, layered structure, and high cation exchange capacity for absorbing water molecules. In contrast, kaolinite has a lower surface area and more stable structure, resulting in slower breakdown. The test water was stirred hourly to mimic the River Avon's current, ensuring a fair test. Both clays demonstrated similar abilities to remove phosphorus from the water without negatively impacting overall water health. Montmorillonite clay would be the better choice for this application because it begins breaking down almost instantly. Designing a structure to hold Phosphorus-Binding Compounds on the outer surface would allow for faster phosphorus absorption as it travels downstream, reducing phosphorus levels with minimal lag time. 24
Creating the Final Stone Design Based on my research into optimal size, shape, and characteristics, I decided to create a lenticular stone with relatively flat dimensions. The stone has a 4 cm diameter and a 1.5 cm base offset, providing a hill-like shape for optimal skipping ability across water. Using various tools like a disc sander, hand sander, wet stone, and manual smoothing, I was able to achieve an evenly distributed hemispheric shape that fits comfortably in the hand. After hardening the clay, I used vacuum forming to create a mould of the shape. The plan was to create half the shape and then cast two pieces to ensure even sides. However, the vacuum pressure dissipated the clay stone, necessitating an alternative method to obtain the desired second side of the mould. 25
Creating the Second Mould Half To accurately create the second half of the mould, I used the newly formed stone shape to cast a clay model, which served as the basis for the second mould piece. This method ensured both mould halves aligned precisely, arguably more accurate than attempting to use the original dissipated clay model. To prevent issues during vacuum forming, I created a wooden square base for the mould, preventing any clay deformation or seepage into the machine. After forming the second mould half, the remaining tasks involved cutting and sanding the pieces to finalize the two-part mould. 26
I tested my final mould by employing techniques from previous studies. I was able to create multiple stone replicas from the mould without causing any damage to it. Each stone produced was accurate to the desired shape, with an overall smooth and well-weighted structure ideally suited for optimal skipping performance. The mould consistently yielded precise stone castings, verifying its durability and ability to facilitate the production of multiple skipping stones with the targeted aerodynamic properties. The successful mould testing confirmed the readiness of this component for the final product assembly stage. Testing the Final Mould 28
To combine 0.15 mg/L (150 micrograms/liter) of calcium with montmorillonite clay, we need to understand how these two substances can bind. The clay's high cation exchange capacity allows binding of calcium cations, which slowly desorb as the clay structure breaks down when exposed to water over time. The calcium ions generally bind to the negatively charged sites on the clay. One approach is to mix the desired calcium solution with dry montmorillonite clay powder. This ensures the calcium is well integrated within the stone material. However, it relies on the complete dissolution of the clay for total calcium release. Since we want to begin decreasing phosphorus levels upon initial entry into the Avon, due to the sites high levels of sewage run off which flows down the stream, binding the calcium to the clay's exterior would be more effective. Therefore, allowing the calcium to bind to pre-formed montmorillonite clay would ensure the calcium attaches to the external negatively charged sites. When added to water, the clay will rehydrate, and the bound calcium will slowly release as the outer layers erode, providing the desired initial phosphorus reduction effect. Creating the Desired Material 1. Create a solution with 0.15 mg/L of calcium, This will be the absorbing solution 2. Test calcium concentration with 5ml sample, this will give us a base test to see if the clay has full absorbed the calcium 3. Add 5 drops of Ca-1 fluid 4. Add 1 scoop of Ca-2 test powder 5. Fill syringe with Ca-3, add slowly till soplution turns blue. Colombo calcium test 6. Quantity of ml added until turned blue shows the calcium content 7. The test changed colour after 6 drops of Ca-3 29
After 30 minutes of the montmorillonite clay being immersed in the calcium solution, I decided to test for any changes. Upon adding one scoop of Ca-2 test powder, the mixture instantly turned blue, indicating no detectable calcium or recognizable calcium remained present in the solution. This binding process occurred much faster than my estimated 24-48 hour timeframe, confirming its effectiveness and quickness. The reliability of this result was further validated by repeating the test three times and consistently observing the same blue color change, suggesting complete calcium depletion from the solution. The high surface area of the clay in relation to the calcium concentration likely facilitated such rapid binding. Although the exact binding duration is unclear, I can confidently state that after 30 minutes, the calcium had definitely bonded to the montmorillonite clay, leaving no residual dissolved calcium in the aqueous solution. Creating the Desired Material 1. Use the Calcium test and determine if calcium is still present in the solution 2. Pat dry the clay 3. Place the clay in a Kiln, ensure it is wrapped in foil 4. Remove and let sit till cool 30
After allowing the stone to harden for 30 minutes, I decided to place it in a 0.1 mg/L (150 micrograms/liter) phosphate solution to determine the success of my concept. Fortunately, the bench-scale testing yielded complete success. After one hour, the stone had reacted with the entire phosphate content in the solution until no visible phosphate remained. I extended the test to 24 hours to ensure a thorough and complete reaction. Additionally, during a trip to Devon, I found an opportunity to test the skipping stone on the River Exe, a waterbody experiencing similar phosphorus and biodiversity issues as the River Avon. This river provided an adequate real-life environment for testing. On my first throw, I achieved a personal record of 15 skips across the river’s surface. I felt immense satisfaction witnessing the success of my creation in a natural setting. The stone effortlessly bounced across the water without any particular throwing technique or methodology from me, demonstrating that anyone can enjoy this product when designed correctly. I hope this creation brings enjoyment and facilitates bonding experiences while providing a short-term shield for the plants and animals across the River Avon by mitigating phosphorus levels. Testing the final Stone - My Result 1. Distilled Water 2. Phosphorus 0.1 mg/L 3. Result after time 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 10 Minutes 1 Hour 12 Hour 24 Hours 31
Reflection As a functional piece, I was overall pleased with the stone's performance for skipping purposes. Its well-designed dynamic proportions allowed it to excel greatly. However, the moulds did leave a slight surrounding line around the stone, requiring additional smoothing. Although this did not necessarily affect its skipping capabilities, it was an aesthetic flaw I would aim to address. The touchstones’ ability to reduce phosphorus levels successfully achieved my goal and could potentially serve as a short-term solution to combat biodiversity threats if used frequently enough. Determining the exact number of stones required per day for maximum effectiveness would necessitate further testing and research beyond the scope of this project. If revisiting this endeavour, exploring a more permanent solution to the phosphorus issues in the River Avon would be ideal, though acquiring the requisite specific data was unattainable within the current timeframe. Healing lives with the skip of a stone... 32
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