Craft Guide using Resins & Glass fibre

Introduction

The combination of polyester resin and glass fiber creates an incredibly versatile material with numerous desirable qualities. It is strong, durable, weatherproof, waterproof, and non-rusting. Additionally, it can be easily molded into virtually any shape or size and adheres well to a wide range of materials, making it ideal for both repair and construction purposes. This innovative material offers sculptors, model-makers, and craft-workers a compelling alternative to traditional materials like metal or wood. In many cases, it proves to be a more practical choice due to its cost-effectiveness and ease of use. For instance, sculptors can opt for the cold-cure "bronze" casting process, which offers a simpler and less expensive method compared to traditional foundry work.

The possibilities of items that can be crafted with these materials are nearly limitless. From costume jewelry, chess sets, and model figures to replica armor, relief maps, theatrical props, scenery, and various types of sculptures, there is a vast range of creative potential. Polyester resin, commonly used in Glassfiber Reinforced Plastic (GRP), is a thick liquid that hardens into a rigid plastic when combined with a suitable catalyst (hardener). It takes the shape of its container, allowing it to be poured or painted into a mold, and once cured, it faithfully reproduces the mold's shape.

This resin is particularly useful for creating detailed castings, and it can be mixed with different fillers, including metal powders, to achieve realistic imitation metal castings. The castings can be painted or self-colored by adding pigment pastes available in various colors. Unlike many other plastics that require high-temperature curing, polyester resins cure at room temperature, making them accessible for home, school, or small workshop projects. While small castings can be made using the resin alone, larger items benefit from the addition of fiberglass materials, significantly enhancing their strength. By layering fiberglass sheets impregnated with resin, a strong laminate is formed that remains lightweight, making it suitable for structures of all sizes.

Although the combination of resin and glass fiber allows for various applications, many techniques are simply variations or permutations of fundamental methods. This handbook focuses on describing these basic techniques while also covering a comprehensive selection of casting and laminating applications. Creative users will discover ways to adapt and modify these techniques to suit their specific projects effectively.

What to do first

GRP offers a significant advantage in terms of project accessibility, as it requires minimal tools, equipment, and workshop facilities. In favorable weather conditions, many projects can be easily carried out in the open air, eliminating the need for a workshop altogether. For most laminating projects, basic tools like brushes, laminating rollers, and plastic buckets are sufficient. In fact, casting projects can be accomplished with even fewer resources, sometimes requiring nothing more than a simple plastic cup to mix the resin. This stands in stark contrast to the substantial investment in equipment and costs associated with working with materials like wood, metal, or sheet plastic.

Because the initial investment in facilities and tools is so low, GRP proves to be a practical option for various scenarios. It can be utilized for one-off jobs, such as creating engineering prototypes or large sculptures, as well as for small-scale "cottage industry" production of craft items.

While the primary cost of working with GRP lies in materials, it's essential not to be deterred by initial impressions. For instance, resin may appear expensive when compared to paints or varnishes. However, it is crucial to recognize that resins used in GRP are structural materials, akin to timber or metal, rather than mere coating materials like paints. Consequently, the cost should be evaluated in the context of its role as a fundamental building component rather than a surface treatment.

Working area

Setting up a suitable workshop for working with GRP is relatively easy, with a few essential requirements to ensure proper curing and safety. The workshop should offer sufficient space, be adequately warm (around 20°C is ideal for correct resin curing), and well-ventilated. Avoid temperatures below 15°C, as the resins won't cure adequately, and temperatures above 30°C will cause rapid curing, leaving little time for application. To avoid the risk of fire, refrain from using oil heaters or electric fires; instead, maintain the temperature with convector heaters or "Dimplex" radiators.

Ventilation is crucial to disperse fumes from certain materials, such as styrene emitted during resin curing. Consider using Resin E, a general-purpose resin with reduced styrene emission, to mitigate this issue. While working outdoors in warm weather can be a viable option, protect your project from rain, as moisture will hinder the resin from curing properly.

A suitable work surface is necessary, and for small projects, a regular workbench or trestle table will suffice. Cover it with polythene, Polyester Film, or brown wrapping paper to protect it from resins and other materials. For larger projects, trestles can be used to support the mold at a convenient height.

As for equipment, you won't need much. The following tools and accessories will be adequate for most projects:

Plastic Cups, Buckets, and Mixing Sticks: These are essential for mixing resins, pigments, fillers, etc. Avoid using polystyrene cups as they dissolve in the resin. Opt for purpose-made calibrated plastic cups that can serve for both measuring and mixing.
Catalyst Dispenser: While paste catalysts don't require a dispenser, a purpose-made safety dispenser is essential for measuring liquid catalyst accurately. For smaller amounts, a measuring syringe can be used.
Plastic Gloves: It's crucial to wear plastic gloves when handling resins or glass fibers. Disposable polythene or rubber gloves are affordable and convenient. Individuals with sensitive skin should consider using Barrier Cream in addition to gloves.
Brushes and Rollers: Brushes are necessary for applying resin, particularly in laminating projects. Use tools specifically designed for GRP to avoid issues with adhesives being attacked by the resin.
Metal Rollers: Metal rollers are only required for laminating and serve to consolidate the resin and glass fiber layers effectively.

By setting up a well-organized workshop and using the appropriate tools, you can create successful GRP projects with ease and safety.

Materials

Various materials are at your disposal for casting and laminating applications, catering to diverse needs, with some specifically tailored for specialized uses. A detailed assortment of these materials can be found in Appendix 1. For the majority of applications, the following products are the ones most likely to be needed.

Table 1: The following table can be used to prorportion catalysts with resin amounts and the temperature you are working within.

East Coast Fibreglass Catalyst Addition Chart
% Of Catalyst to Resin	4% Catalyst	3% Catalyst	2% Catalyst	1% Catalyst
Temperature	5-13° C	13-15° C	16-20° C	20-35° C

RESIN	CATALYST	CATALYST	CATALYST	CATALYST
500g	20ml	15ml	10ml	5ml
1Kg	40ml	30ml	20ml	10ml
2Kg	80ml	60ml	40ml	20ml
3Kg	120ml	90ml	60ml	30ml
4kg	160ml	120ml	80ml	40ml
5kg	200ml	150ml	100ml	50ml
6kg	240ml	180ml	120ml	60ml
7kg	280ml	210ml	140ml	70ml
8kg	320ml	240ml	160ml	80ml
9kg	360ml	270ml	180ml	90ml
10kg	400ml	300ml	200ml	100ml

For most projects

Resins: In all laminating and casting applications, a resin is essential, with polyester being the most commonly used (although polyurethanes and epoxies are also viable options). Resin A, known as Lay-Up Resin, holds widespread usage as a general-purpose resin suitable for both resin-casting and impregnating glassfibre during laminating.

Catalyst: It is crucial to catalyze ALL resins, including Gelcoat, with hardener before use, as uncatalyzed resin will not harden. Some resins come with their own specific catalysts, such as Fastcast and epoxies. For polyester resins, catalysts are available in paste or liquid form.

Pigments: Pigments are added to the resin to achieve self-coloring in laminates and castings. You can find pigment pastes in a wide range of colors to suit your preferences.

Brush Cleaner: Brush Cleaner is used to remove uncured resin from brushes and tools. However, it may not be necessary for certain casting projects where only mixing sticks are utilized.

Barrier & Cleansing Creams: To safeguard and clean the skin while working with resins or glassfibre, it is essential to use Barrier Cream in conjunction with gloves. Cleansing Cream (NOT Brush Cleaner) should be used to remove resins and other substances from the skin effectively.

Mainly for laminating

Resin B:

Gelcoat resin is primarily utilized in laminating applications, serving to create the smooth outer surface of the final laminate.

Glassfibre:

Glassfibre is mainly employed in crafting laminated structures, though it can also reinforce large castings if necessary. You can choose from a variety of glassfibre mats, ravings, and fabrics, each offering different strength-to-weight ratios. Chopped Strand Mat is one of the most commonly used options.

Release Agents:

Resins have strong adhesive properties and can bond firmly to various surfaces like wood, GRP, steel, plaster, and hardboard. However, when using a mold made from these materials, it's essential to prevent the resin from sticking by applying a parting agent or Release Agent. In contrast, flexible molds typically don't require these agents, as most flexible materials commonly used are self-releasing compounds.

Mainly for casting

Insert filler powders are introduced to lay-up resin to create a "slurry" for resin-casting or to modify the resin's texture. While not always necessary for most laminating projects, fillers can be added to achieve specific surface effects, such as using metal powders for replicating armor during laminating.

Safety Precautions:

To ensure safe handling of materials for resin-casting and laminating, it is crucial to observe these simple rules:

Always work in a well-ventilated area.
Never smoke or use naked lights or fires in the work area.
Always wear gloves to prevent materials from coming into contact with the skin, especially the eyes or mouth.
Never swallow any of these materials.

Handle the catalyst with particular care, as it is both inflammable and corrosive. Avoid skin, mouth, or eye contact. In case of accidental contact with the skin, wash the affected area immediately under running water. If it comes into contact with the eyes, flush them with running water for at least 15 minutes and seek medical attention.

When using glassfibre, resins, and ancillary materials, ensure that young children are closely supervised to promote safe usage.

Mould Making

GRP materials offer a wide array of techniques, primarily falling into two categories: casting and laminating. For both methods, the initial requirement typically involves a mold.

Mold options include purchasing ready-made molds, especially for casting items like chess pieces, or crafting your own from original models. The preferred mold materials for casting are self-releasing flexible compounds, encompassing latex materials, hot-melt compounds, and cold-cure synthetic rubbers. While the latter may be pricier, they boast greater durability and superior reproduction quality. Original models can be fashioned from various materials, such as clay, plaster, plasticine, glass, porcelain, or metal. However, avoid using ferrous metals with latex and ensure heat-resistant materials if employing hot-melt compounds.

Plaster molds can also be used, particularly for large items that would be excessively costly in other materials. For producing simple geometric shapes, it is possible to create a suitable mold directly from plywood, hardboard, or even cardboard, ideally covered in Polyester Film. In laminating, flexible molds are rarely used; instead, rigid molds made from GRP are commonly chosen. To create such a mold, laminate over the model (often referred to as a "former" or "plug"). The plug can be made from various materials, as long as it is precise, sturdy, and has a finely finished surface. A small plug can be modeled in clay or built from plywood or fiberboard, while a larger plug might have a wooden framework covered with plywood, hardboard, clay, or plaster reinforced with wire netting or hessian, or a combination thereof. The choice of materials depends on the specific project requirements. To ensure a faithful reproduction, the plug surface must be flawlessly smooth and devoid of defects or blemishes. Nails should be securely hammered in, screws should be countersunk and covered with filler, and all dents, joints, and seams should be diligently filled, preferably with resin putty. Wooden plugs can be further enhanced with Furane Resin, a coating resin that imparts a highly glazed surface.

If the plug has deep draughts or undercuts, a rigid mold must be crafted in two or more sections to avoid the laminate locking into the undercuts and becoming impossible to remove. This approach is common for model boat hulls, where the mold may be split along the keel line to accommodate "tumble-home" at the stern. These sections require flanges for bolting together. To create the flanges, "fins" should be added along the split-lines of the plug, made from suitable materials like thin aluminum sheet. Alternatively, the plug itself can be divided into sections for mold construction.

Latex dipping rubber

Latex, a natural and air-drying liquid rubber, serves as an excellent material for crafting thin, elastic, and self-releasing molds. It works best for reproducing small, uncomplicated models with minimal fine detail, making it a popular choice for items like chess pieces.

Using latex is incredibly straightforward, requiring no prior preparation. The original model, or "former," is merely dipped into the liquid rubber, allowing a thin film of latex to cling to it. The dipping process is repeated until the desired thickness is achieved. Formers can be made of various materials, including glass, aluminum, porcelain, polyester resin, clay, or plaster. However, avoid using copper, brass, bronze, or ferrous metal formers, as a chemical reaction may occur, compromising the rubber. Similarly, do not store latex in containers made from these materials. Plaster formers are considered one of the best choices and should be thoroughly dry before use. It's recommended to attach a wire or wood handle to the base of the former for easy dipping.

When dipping the former into the latex, do so gently and wait a few seconds before removing it slowly to prevent air bubbles from forming, which could affect the mold's quality. If the latex has been shaken before use, allow it to settle before starting the mold-making process. When using plaster formers, you can create the mold in a single dip by suspending the former in the latex solution for approximately 35 minutes for a chess piece up to about 6" high. After dipping, let the latex mold dry completely for about 24 hours before removing it from the former. Avoid speeding up the drying process by placing the mold in front of a fire, as excessive heat can cause the latex to lose its elasticity. For faster drying, you may gently hold the mold about 12" from a mild source of hot air, such as a hair dryer set to its lowest setting.

Once fully dry, carefully peel the latex mold from the former. To make the peeling process easier, rinse the mold in diluted washing-up liquid or dust it with talc.

Vinamold & Gelflex Hot-Melt Vinyl's

Vinamold and Gelflex are versatile, reusable, self-releasing synthetic rubbers based on vinyl resins. They offer an excellent choice for creating molds suitable for a wide range of casting applications, including epoxies, polyesters, plaster, and even fine concrete for decorative paving. With up to ten castings obtainable from each mold, these vinyl materials are highly efficient.

Vinamold comes in strip form, requiring cutting before melting, while Gelflex is supplied in convenient granulated form, ready to use. Different grades of these materials are available, offering varying degrees of flexibility and durability. More flexibility is advantageous for complex-shaped original models, whereas greater durability becomes crucial when multiple castings are needed from the same mold. Intermediate flexibility levels can be achieved by mixing different grades.

Typically, release agents are not necessary, except for porous originals, which should be sealed with heat-resistant varnish. Wooden formers benefit from a two-part polyurethane varnish coating, allowed to cure for about seven days. For stone or plaster formers, soaking in water and then wiping dry before mold-making prevents rubber from locking into pores while retaining the texture. A damp clay model serves as an ideal former, but it should not be too wet to avoid bubble formation in the mold during the pouring process.

Using a double-skinned melting pot, heat the vinyl material slowly until it turns into a smooth, thin liquid with a creamy consistency. Stir frequently while melting and ensure proper ventilation during this process. Avoid overheating, as it may lead to decomposition or even ignition. Once melted, pour the compound between the former and retaining walls slowly and continuously to avoid trapping air bubbles. It is helpful to warm the former before pouring to reduce the risk of air voids. After pouring, allow the mold to cool overnight before it is ready for casting.

When the mold is no longer needed, it can be washed, cut up, and melted down for reuse, making these synthetic rubbers a cost-effective and sustainable choice for creating molds in various casting applications.

Masturing Cost-cure rubber

Mastermould stands out as an exceptional cold-curing, self-releasing silicone rubber compound. Unlike materials that can be melted down and reused, silicone rubbers set at room temperature through a chemical reaction with the addition of catalyst (hardener). They offer outstanding reproduction of fine detail with minimal shrinkage, making Mastermould ideal for low-volume mass production, yielding 40 or 50 castings easily. Depending on the complexity of the molding, it is possible to obtain a hundred or more resin castings (with materials like plaster, the number of possible castings is even higher).

Similar to hot-melt materials, retaining walls are necessary around the former. However, as the silicone rubber is cold-curing, heat-resistant walls are not required. The material is inert, allowing for the use of various materials for formers and retaining walls, including plasticine, polystyrene foam, and even children's construction toys like "Lego." To ensure smooth molding, it is advisable to seal porous formers with Release Agent No 1, polyurethane varnish, or cellulose lacquer. The varnish should be allowed to cure thoroughly for at least seven days before making the mold.

To prepare Mastermould, add the catalyst to the base material (one part catalyst to ten parts base by weight) and mix thoroughly. Since the base and catalyst have different colors, proper mixing will result in an even color. Avoid excessive stirring to minimize air bubbles. After allowing the mixture to stand for a few minutes to let any trapped air escape, pour the compound around the former (not directly onto it). Cold-cure rubber offers the advantage of applying an initial layer with a brush to ensure fine detail is adequately filled. After leaving this layer for about five minutes, pour the rest of the compound to cover the former. Allow the mold to cure for about 24 hours without removing the former. Afterward, the former can be removed, but it's best to let the mold continue curing for another 24 hours before casting.

BUTTER-ON MASTERMOULD: A special thyrotrophic additive is available for use with Mastermould, transforming it into a stiff "butter-on" paste that can be applied with a palette knife. This method can be more cost-effective, especially for larger molds.

To use the thixotropic material, first, mix up Mastermould as described earlier, and brush an initial layer on the former to ensure fine detail is filled. Then, mix the thixotropic additive with the rest of the compound (4g additive per 100g mixture). The mixture will thicken immediately and can be applied right away. Use a palette knife to apply the compound in several layers, pressing the first layer firmly to fill gaps and expel trapped air in voids. You can use a cocktail stick as a probe to check the mold's thickness, which should be built up to a minimum overall depth of half an inch.

Two-part moulds

Creating a mould in two or more parts becomes necessary when dealing with a complex model. While it's nearly impossible with Latex, materials like Mastermould make the process fairly straightforward. One approach is to start with a smooth surface like Melamine or Formica and build a retaining wall using "Lego" bricks. Fill this enclosure with plasticine, ensuring a firm press down. The result is a plasticine slab bordered by "Lego." To achieve a smooth surface, gently release the slab from the Melamine, turn it upside-down, and expose a completely smooth and flat surface.

Next, place the original model (former) on the flat surface and carefully scribe around its outline using a fine stylus or needle. After removing the former, carve out the plasticine within the outline, creating a cavity for the former to rest in. The former should now be half-buried in plasticine, and any gaps can be filled using small pieces of plasticine. Creating locating lugs in the mould involves making depressions in the plasticine at about 2" intervals. Alternatively, dome-headed screw-covers meant for mirrors can be used as lugs. If desired, the plasticine surface can be coated with a thin layer of diluted PVA Adhesive to facilitate cleaning off any plasticine residues adhering to the mould.

Once the retaining wall's height is built up by adding more "Lego" bricks, the Mastermould compound can be poured in. The mixing and pouring process remains the same as previously described. Allow the rubber to cure for 24 hours.

Now, for the second part of the mould, invert the entire unit while carefully removing the plasticine without disturbing the former. Any remaining traces of plasticine can be gently removed. If the retaining walls were removed earlier, rebuild them to an appropriate height for pouring the second layer of Mastermould. Although Mastermould is self-releasing from most materials, it adheres firmly to itself, so a release agent is necessary. Release Agent 1711 is recommended, which can be sprayed onto the rubber surface. Immediately pour the second layer of Mastermould and let it cure for 24 hours.

After curing, the two halves of the mould should separate easily, allowing you to remove the former. However, before casting, it's essential to create a suitable pouring hole and vents to allow trapped air to escape. Use a scalpel or fine craft knife for this purpose. For very fine vents on small model figures, such as 54mm scale models, a hypodermic syringe needle can be used to pierce the mould and remove a thin core of rubber. The vents should lead to areas where air pockets are likely to form, such as small protrusions on the model, such as the nose, ears, and fingers of a model figure. Finally, use the locating lugs to align the two halves of the mould, secure them together with tape, string, or elastic bands, and your two-part mould is now ready for casting.

Casting

A flexible mould offers excellent adaptability to handle complex shapes and tackle challenges like undercuts. However, if the mould is excessively flexible, it may deform under the weight of the resin, resulting in an unexpected casting shape. This issue is more likely to arise when using vinyls or "butter-on" Mastermould. To minimize this problem, it's beneficial to make the mould walls as thick as possible. Nevertheless, a more effective approach is to provide additional support to the mould using an outer container or "case."

The "case" serves to reinforce the mould and maintain its shape during casting. While a cardboard or fibreboard box can sometimes suffice, it is often more practical to create the case using plaster or a glassfibre laminate, which can be molded to follow the contours of the flexible mould. It is important to construct the case before removing the former from the mould, ensuring proper support during the casting process. This technique helps achieve more consistent and accurate castings, even when dealing with intricate or intricate shapes.

Plaster moulds

While flexible mould materials deliver excellent results and convenience, they can be costly when used in large quantities. Therefore, for creating moulds from large models, such as life-size figures, alternative materials are often preferred. A common method involves using plaster, but it does come with some drawbacks. Plaster is not flexible, making undercuts and complex shapes problematic, necessitating the mould to be divided into several sections. Moreover, most plaster moulds can only be used once, making them "waste" moulds. Additionally, as plaster firmly bonds to the resin, a parting agent or Release Agent is required to facilitate mould removal.

To create plaster moulds suitable for both casting and laminating applications, clay models are typically used as the originals. These clay models can be coated with petroleum jelly or Release Agent No 1 to aid in mould removal. To minimize the number of sections needed, clay walls or thin metal dividers can be added to separate the mould sections, and efforts can be made to design the original model to avoid undercuts whenever possible.

The process of applying plaster should begin with a thin coat mixed to a creamy consistency. This ensures the fine detail is accurately reproduced without the plaster draining from the model. Subsequent coats can be thicker and built up to achieve the desired depth. For instance, a mould around 12" in diameter should have a thickness of at least half an inch, with larger moulds requiring proportionately more depth. To strengthen the plaster, a scrim of Hessian or, for maximum strength, glassfibre can be incorporated into the mix. Adding PVA Adhesive to the mix also enhances the plaster's strength.

After allowing the plaster to cure for at least a day, it can be carefully removed from the model. For optimal results, leaving it for an additional two to three days will ensure complete hardening. Before use, the plaster mould's surface should be sealed with polyurethane varnish or, even better, Release Agent No 1. To prepare the plaster mould for casting or laminating, follow the same method detailed below for GRP moulds, including the use of release agents.

GRP moulds

For most laminating projects, a rigid GRP (Glass-Reinforced Plastic) mould is the ideal choice. This type of mould is created by laminating glassfibre over a former, also known as a "plug." While a simple geometric plug made from flat sheets may be faced with self-releasing polyester film, in most cases, the plug requires prior treatment with release agents before laminating the glassfibre mould.

If the plug is made of porous materials, like plaster, it should be sealed with Release Agent No 1. Then, it is essential to apply four to six coats of Release Agent No 3, allowing each coat to thoroughly harden for about an hour before buffing and applying the next one. Finally, a surface coat of Release Agent No 2 is used. The mould is produced using the same technique as any other glassfibre lay-up: a layer of gelcoat, followed by successive layers of glassfibre impregnated with Resin A. Detailed instructions for this process can be found in the section on Laminating Technique. The primary difference is that the mould needs to be much thicker (often twice as thick) than the finished item. Large moulds can be expensive, but incorporating strengthening ribs and stiffeners can help reduce costs. Add these ribs after the mould has partially cured to prevent the surrounding laminate from leaving impressions on the mould surface.

If the mould consists of two or more sections, flanges are needed (preferably about 75mm wide and at least 50% thicker than the rest of the mould), which can later be drilled so that the parts can be bolted together. It is essential to allow the mould to cure completely, preferably for at least two weeks, before removing it from the plug to avoid distortion. The size of such a mould has no limitations; commercially, GRP moulds are used for items such as boat hulls measuring thirty or forty feet long. However, for added support, a large mould can benefit from being bonded onto a wooden framework. After giving the mould some time to "breathe" for a few days, it can be filed or sanded to address any imperfections, although there should be few if the plug was correctly finished. Finally, the mould must be treated with release agents before use.

Other moulds

For certain applications, like clear casting, polypropylene or polythene containers can be used as moulds. These containers are readily available for various foodstuffs and household products and are self-releasing. However, it's important to avoid using polystyrene containers, as they will dissolve when in contact with polyester resin.

"Direct" Moulds

As mentioned earlier, it's possible to create a mould directly without the need for an original model or former. This approach is usually suitable for relatively simple shapes, such as a box, trough, or basic geometric forms for clear casting. Typically, such moulds are constructed from sheet materials like plywood, hardboard, metal, glass, or, for smaller items, cardboard. Whenever possible, it's advisable to face the material with polyester film to facilitate easy release. Alternatively, the material should be treated with release agents. Some plastic sheet materials may already be self-releasing, but it's essential to avoid using ABS, polystyrene, or acrylates (e.g., Perspex) as they can be attacked by polyester resins. In some cases, polystyrene foam materials can be used if adequately protected from the resin. To achieve this protection, you can spray the foam with latex thinned with distilled water, although this method may not always be entirely reliable.

RESIN CASTING

ESTIMATING QUANTITIES:

Calculating the exact quantities of materials needed for casting can be challenging due to the variability in resin-to-filler ratios and the consistency of the resin/filler mix. The table below provides approximate resin quantities required for various mould sizes and different resin-to-filler ratios. To determine the volume of a mould, fill it with water and then empty the water into a measuring jug after ensuring the mould is dry.

Casting from Latex Moulds:

The following method outlines the usual procedure for casting small items like chess pieces using latex moulds. This technique can be applied to most casting projects, but specific material quantities may vary for different projects.

Prepare the Moulds: Place the moulds upside-down in a suitable holder, such as an upturned cardboard box with holes cut in the bottom to create a rack.
Mixing the Resin and Filler: Half-fill a plastic mixing cup with lay-up resin and another cup with filler powder. This will provide a convenient working quantity for a small casting and maintain equal volumes of resin and filler. Adjust the mix consistency to suit your specific requirements. If you want to add color to the casting, stir in enough pigment paste to achieve the desired hue, up to a maximum of 10% pigment (using more may affect resin curing). Note that the color may change once the filler is added.
Combining Resin and Filler: Sprinkle the filler into the resin and stir thoroughly. Allow the mixture to sit for a short while to disperse any air bubbles. Tap the side of the cup gently to bring bubbles to the surface. Afterward, add the catalyst to the mixture, stir, and let it stand for one or two minutes before pouring into the upturned moulds.
Removing Air Trapped in Undercuts: Gently squeeze each mould to force out any air trapped in the undercuts. If necessary, top up the mould with more resin mix, but be cautious not to fill over the flange.
Allowing the Casting to Set: Leave the mould to set, which typically takes about half an hour in a warm room.
Removing the Mould: Once the casting has hardened, carefully peel off the mould. If using a homemade mould, rubbing diluted washing-up liquid over it may make the removal process easier.
Preparing the Mould for Reuse: Wash out the mould with warm, soapy water, dry it thoroughly, and dust it with talcum powder before reuse.

Figure 1: Resin and glass/fiber offer endless possibilities for various projects, including models, replicas, sculptures, and various craftworks. Curtacy of FreePik found at this link.

Casting from other flexible moulds

Casting from different types of flexible molds follows a similar procedure with some minor variations. As before, mix lay-up resin and filler powder to the desired consistency, add pigment if needed, and catalyze the mixture. Let it stand briefly to disperse any air bubbles before pouring it into the mold. For flat and open molds, like wall plaques, it can be helpful to brush a layer of resin into the mold to ensure all details are filled and no air is trapped in the undercuts. Then pour the rest of the mix. For larger castings, avoid pouring all the resin at once to prevent excessive heat generation during the curing process, which could cause cracks. Instead, pour the resin in layers, letting each layer partially cure before adding the next one.

For larger castings, reinforce them with materials like Hessian or preferably glassfibre. Apply Resin A on the back of the casting, place a piece of glassfibre mat, and gently push it into the wet resin with a brush. Use a stippling action to thoroughly impregnate the glassfibre. Unlike smaller castings, a laminating roller might not be suitable, so stippling is the best way to compress the glassfibre. Repeat the process if additional layers are needed.

Allow the casting to set for about half an hour in a warm room, but the time may vary based on factors like catalyst proportion and temperature. Once the casting has hardened, carefully remove it from the mold. Clean the mold with warm, soapy water, dry it thoroughly, and dust it with talcum powder before using it for further castings. For vinyl molds that will be melted down, ensure they are clean before cutting them up and re-melting. When casting from plaster molds, follow the same procedure.

The procedure mentioned earlier is also applicable when casting from plaster molds. However, there is one essential difference - plaster molds, or any molds made from porous materials like wood or fiberboard, require treatment with release agents. Failing to do so will result in the casting bonding tightly to the mold, making it impossible to remove. To prevent this, first, seal the mold with shellac, polyurethane varnish, or preferably, Release Agent No 1. Next, apply a wax release agent, such as Meguiars or Honeywax, to ensure smooth and easy release of the casting.

Figure credit: Prostoolah curtacy of freepik found in this Link

Metal casting

Using powdered metals as fillers produces castings with a remarkably realistic metallic finish. The process is quite similar to using regular filler powder, but with one crucial distinction - the resin is catalyzed BEFORE adding the metal powder, as a safeguard against the catalyst's corrosive effects on the metal. For metal castings, it's essential to use 2ml of catalyst per 100g of resin.

The quality of the finish improves as the proportion of metal to resin increases. In general, a 50/50 mix by volume is considered the minimum ratio for a satisfactory result. Initially, the finished casting may not appear particularly metallic, as a thin layer of resin dulls the surface. However, by gently buffing this layer with wire wool and applying metal polish, the desired realistic metallic sheen emerges.

For added versatility, different metal powders can be blended together. A combination of aluminum and a touch of brass, for example, yields a convincing simulation of old, tarnished silver. To ensure a smooth integration, the powders should be mixed beforehand, before they are added to the resin.

For an aged effect, consider rubbing graphite powder onto the finished casting. For a more pronounced result, mix the graphite with the metal powder in a 1:10 ratio by weight before adding it to the resin.

To achieve the appearance of forged steel and impart an appealing antique look to reproduction armor crafted from aluminum, apply a light coating of "grate black," such as "Zebrite," and seal it with a spray varnish. Interestingly, the spray fixative designed by Letraset for rub-down lettering works remarkably well as a suitable varnish for this purpose.

For further experimentation with aging effects, consider coating the surface with leather or wood dyes mixed with a small amount of acetone. Gently wipe off the excess with a cloth lightly dampened in acetone to achieve unique and captivating results.

Clear casting

Clear casting resin serves a variety of purposes, from embedding objects in transparent plastic to creating decorative paperweights, preserving medical specimens, and crafting costume jewelry. When working with clear casting resin, it's crucial to select appropriate molds to ensure successful results.

Avoid using flexible rubber molds, as they allow air to seep through to the resin, interfering with the curing process and leading to a tacky surface. Instead, consider using glass or treated plastic molds. Glass molds should be treated with a release agent to prevent sticking.

Creating molds from card, wood, or fiberboard is also possible, but make sure to cover the surfaces with self-releasing Polyester Film and seal the joins securely to avoid resin leaks. Polythene cartons can be employed as molds, but steer clear of polystyrene, as it will dissolve when in contact with the resin.

Here's how to proceed with making the casting:

Catalyze the resin following the instructions in the table provided.
Pour the catalyzed resin into the mold to form a base layer.
Once the base layer reaches a firm consistency, place the specimen on it and pour a little more resin around it. For lightweight specimens, use a few drops of resin to glue them to the base layer to prevent floating.
Depending on the size of the casting, you may choose to cover the specimen in one pouring for very small castings or build it up in multiple layers for larger castings. This prevents excessive heat generation during curing, which could lead to cracks.
Once the final layer has set firm (or "gelled"), cover it with Polyester Film or cellophane to exclude air and prevent a tacky surface during curing.
Allow the casting to harden, and then carefully remove it from the mold.
If desired, further shape or polish the casting using suitable methods to achieve the desired final appearance.

With clear casting resin, you can create captivating and unique objects with embedded specimens, suitable for various decorative, preservation, and jewelry applications.

Preparing specimens for clear casting requires careful attention to ensure optimal results. Here's a step-by-step guide to the process

Insects:
- Remove natural oils by dipping the specimen in a grease-solvent like acetone (remember that acetone is highly flammable).
- Allow the specimen to dry completely. For improved results, dip it in uncatalyzed resin and let it drain overnight, creating a thin film that prevents shrinkage and "silvering."
Flowers:
- Dry the flowers thoroughly by placing them in a container filled with silica gel crystals or dry fine silver sand.
- Leave the flowers in a warm atmosphere for several days to ensure complete drying. The drying time may vary for different plants and should be determined through experimentation.
- Seal the dried flowers with polyurethane varnish or hair lacquer to protect them. Note that some flowers may fade more than others during drying.
- Optionally, you can dip the dried plant in uncatalyzed resin and allow it to drain overnight for added preservation.
Paper items (e.g., postage stamps):
- Seal paper items with a thin coat of polyurethane varnish or hair lacquer to protect them during embedding.
Coins, medals, pebbles, shells:
- Wash these items thoroughly to remove dirt or grease.
- Ensure they are completely dry before proceeding.
- Dip the items in uncatalyzed resin and let them drain overnight before embedding.
Polystyrene models, etc:
- Coat polystyrene models with a thin layer of two-part epoxy laminating resin.
- Allow the epoxy to cure for at least seven days before proceeding with embedding.

For other casting or laminating processes, refer to the "Finishing" section for specific guidelines.

By following these preparation steps, you can ensure that your specimens are clean, dry, and free from oil or grease, ready to be beautifully embedded in clear casting resin.

Enhancing a clear casting can be achieved by incorporating an opaque layer, typically using pigmented base resin. This clever technique creates an attractive contrast with the rest of the casting. When using an inverted mould, remember to pour the layers in reverse order, with the last layer becoming the base of the finished casting. Using pigmented Resin A for the opaque base ensures a smooth, tack-free surface.

Clear Casting Resin offers a wide range of creative possibilities for resourceful users. For instance, it can be used to craft lifelike ponds, streams, and other water effects in model landscapes. To achieve this, simply add 2gm of accelerator per 100gm of resin and thoroughly mix BEFORE catalyzing. However, exercise caution when using the accelerator, as it can be hazardous. Make sure to read the Safety Information on Accelerator in Appendix 2 for proper handling.

A safer alternative for reducing surface tackiness is to apply a thin final coat of two-part epoxy laminating resin, which can effectively provide a smooth finish.

Moreover, clear castings can be utilized to construct three-dimensional geometric forms like dodecahedrons using card covered with polyester film. These geometric forms can then serve as moulds for creating captivating abstract castings, especially when the resin is lightly tinted with pigment. Experimenting with pigment drops and allowing them to spread unevenly in the resin can yield intriguing effects. Additionally, loosely lining a container with polyester film not only shapes the casting according to the container but also reproduces the folds and ripples in the film, leading to captivating results. Unleash your creativity by exploring various other opportunities and possibilities through experimentation.

Polyurethane resin casting

Fastcast is an excellent example of a polyurethane casting resin known for producing strong, durable castings with high definition and excellent reproduction of fine details from flexible rubber moulds. It is particularly useful for small-scale models and components and is widely favored by commercial model-makers for crafting high-quality model kits. Although slightly more expensive than polyester resin, its benefits include rapid setting and easy mixing and measuring. Additionally, for home users, polyurethane resin has the added advantage of being odorless, as it does not emit styrene fumes commonly associated with polyesters.

When working with polyurethane resin, it's important to note that materials self-releasing from polyester resin tend to adhere firmly to polyurethane. Therefore, all moulds must be sprayed with a special release agent (Release Agent 1711) to ensure easy separation from the finished casting. It's worth mentioning that polyurethane resin is sensitive to moisture, so it's crucial to use completely dry filler powders, moulds, mixing containers, and tools. Conventional filler powders that absorb atmospheric moisture should be avoided, and non-absorbent fillers like 3M Glass Bubbles are recommended.

The process of using Fastcast involves mixing equal amounts of the two-part resin kit in separate containers and stirring thoroughly before combining them. Once mixed, the resin should be promptly poured into the mould, as it gels within two or three minutes. Larger castings can be poured all at once due to Fastcast's low exotherm, but if multiple pours are necessary, they should be done within ten minutes to ensure proper bonding between layers. After 30 minutes, the casting can be removed from the mould, but it's advised to allow another two hours of curing at room temperature for complete hardening.

For larger castings, polyurethane foam materials can be used as backing. To achieve this, the workshop must be well-ventilated due to the cyanide fumes produced by the foam mix. Once the foam has cured for 24 hours, any exposed foam surface can be coated with additional layers of Fastcast.

Polyurethane castings can be easily painted after thoroughly washing away traces of the release agent. Enamels, acrylics, oil paints, and aerosol cellulose paints can be used for painting. To bond polyurethane castings together or to other materials like metal, "five-minute" epoxies or cyano-acrylate adhesives are suitable choices.

When using fibreglass materials, there is no "correct" method, and variations of the basic technique can be employed to suit individual projects. Sculptor Steve Melton used a unique method for casting from a 15' clay figure, using plaster to partition sections and moulding brackets to hold the mould sections together. After hardening, the mould sections were assembled and used to create the finished sculpture.

For laminating, you will need additional tools like metal laminating rollers and materials like gelcoat, glassfibre (Chopped Strand Mat), and release agents. Laminating requires applying gelcoat to the mould first, followed by layers of Resin A mixed with pigment and glassfibre. The number of layers and reinforcement can be adjusted based on the desired thickness and strength of the laminate. After curing, the laminate can be trimmed, and the casting process can be further customized with various techniques and formers.

Preparing Specimens for Clear Casting:

For successful clear casting, specimens that are to be embedded must be clean, dry, and free from any oil or grease. Different types of specimens require specific preparation methods:

Insects: Remove natural oils by dipping the specimen in a grease-solvent such as acetone (remember that acetone is highly flammable). Afterward, allow the specimen to dry completely. For optimal results, dip the insect in uncatalyzed resin and let it drain overnight. This creates a thin film that prevents shrinkage and "silvering" on the finished casting.

Flowers: Thoroughly dry the flowers by placing them in a tray filled with silica gel crystals or dry, fine silver sand. Leave them in a warm atmosphere for several days. After drying, seal the flowers with polyurethane varnish or hair lacquer. Note that some plants may take longer to dry than others, so experimentation is advised.

Paper Items (e.g., postage stamps): Seal these items with a thin coat of polyurethane varnish or hair lacquer.

Coins, Medals, Pebbles, Shells: Wash these objects to remove any dirt or grease and ensure they are completely dry. Dip them in uncatalyzed resin and let them drain overnight.

Polystyrene Models, Etc: Coat these models with a thin layer of two-part epoxy laminating resin and allow it to cure for at least seven days before embedding. Additionally, refer to the section on "Finishing" for other casting or laminating techniques.

By following these preparation steps, you can achieve high-quality clear castings that preserve and showcase the embedded specimens effectively.