Omar Khalid
Casting plastic miniatures is a challenging but rewarding process. It involves creating a mould, which can be made from various materials such as silicone, clay, or Play-Doh, and then using this mould to create detailed miniature sculptures. The process requires precision and attention to detail, as even a slight misstep can result in slippage or air bubbles that ruin the final product. There are legal considerations to keep in mind as well, as casting copyrighted miniatures without permission can lead to legal repercussions. With the right tools, knowledge, and caution, casting plastic miniatures can be a satisfying endeavour.
| Characteristics | Values |
|---|---|
| Molds | Two-part molds are recommended for miniatures. One-piece molds are suitable for simple shapes. |
| Mold Materials | Play-Doh, clay, Green Stuff, plaster of Paris, resin, silicone, and polyurethane are all suitable mold materials. |
| Casting Materials | Resin, pewter, and plastic are commonly used for casting miniatures. |
| Techniques | Spray the mold with a release agent, wrap with tape, and use wood to distribute pressure. Mix casting material well, degas, and pour into the mold slowly, rolling to remove air bubbles. |
| Considerations | Creating copies of copyrighted miniatures may violate intellectual property rights. |
| Suppliers | Smooth-On, Iron Wind Metals, and Michael Noe are mentioned as suppliers for molds and casting services. |
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What You'll Learn
Using silicone rubber moulds
Silicone is a great material for moulding miniatures because it doesn't stick to things, making it ideal for casting a wide range of materials, including plastic, resin, plaster, and wax. However, silicone does stick to itself, so it's important to ensure that the mould is properly sealed between castings.
When creating a silicone mould, it's important to accurately measure the materials using a digital scale. It's recommended to mix a little more than you think you'll need to fill the mould, as it can be difficult to mix a new batch quickly. Before casting, inspect the mould for any holes or leaks, as even a tiny pinhole can result in leaks.
To prevent leaks, you can seal the mould with a release agent. Common release agents include PVA, liquid floor polish wax, SuperSeal, Mold Soap, EZRelease, and Universal Mould Release. After applying the release agent, pour in the silicone and wait for it to cure. Once cured, you can remove the mould and apply another coat of the seal and release agent.
For a two-part silicone mould, after the second piece has cured, you can remove the master and inspect the mould. You can then clap the mould together and cast your final parts. It's important to note that different materials have varying cure times, viscosities, and surface tensions, so be sure to read up on how to prepare the mould properly.
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Preparing the mould for casting
Measure and Cut the Mould Box
First, measure the width and height of the object you plan to mould. Add at least one inch to the width measurement. For the height, ensure it is significantly taller than the object, but there is no specific amount needed. Cut four pieces for the sides and one for the bottom to create a box that accommodates your object.
Secure the Object
Attach the object securely to the bottom piece of your mould box using hot glue. This will ensure that it remains in place during the casting process.
Assemble the Mould Box
After securing the object, attach the side panels to the bottom piece using hot glue. Ensure that all gaps and seams are filled with hot glue to create a sealed container for your mould material.
Prepare the Mould Material
For silicone moulds, mix your chosen silicone product according to the manufacturer's instructions. A popular option is to use a 1-to-1 ratio silicone mould product, such as Oomoo 30, which is affordable and easy to mix. Combine equal parts of the product in two separate cups, and then pour them together into a larger container. Mix thoroughly, scraping the sides and bottom of the container to ensure a consistent mixture.
Fill the Mould Box
Pour the mixed silicone into the mould box, ensuring it covers your object completely. If needed, use Lego bricks or small containers to support the mould box and contain the silicone.
Finalize the Mould
Before the silicone sets, ensure that the mould is free of air bubbles. You can do this by gently tapping or vibrating the mould box to bring any trapped air bubbles to the surface. Once the silicone has cured, carefully remove your original object from the mould.
Additional Tips
If you're looking for an alternative to silicone, you can use a quick-curing 2-part filler like car body filler, which is a form of filled polyester resin. Another option is to use a product like Gorilla Glue, which is a one-component uncured polyurethane that doesn't require a mould release agent and is readily available at hardware stores.
Now that your mould is prepared, you can move on to the next step of casting your plastic miniatures!
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Choosing the right casting material
- Silicone Moulds: Silicone is a popular choice for creating moulds due to its flexibility, low cost, and ease of use. It can be easily found in hardware stores and online. Silicone moulds are ideal for casting small plastic miniatures as they can withstand the curing process and allow for easy part ejection. However, they typically last for around 20 castings.
- Urethane Casting: Urethane casting, also known as polyurethane casting, is a widely used method for creating small plastic miniatures. It offers a good level of detail and is cost-effective compared to injection moulding. Urethane casting allows hobbyists to make multiple identical duplicates of their original master pattern. The process involves using a flexible material, usually silicone, to create the moulds, which can then be filled with polyurethane resin to create the miniatures.
- Polyurethane Casting: Polyurethane is a versatile casting material that can be used for both mould-making and casting. It is a one-component uncured polyurethane, and it does not require a mould release agent when used with silicone moulds. Polyurethane casting offers low costs and the freedom to use homemade master patterns.
- Clay and Hand-Sculpting: For those who enjoy the hands-on approach, hand-sculpting unique pieces from clay or other sculpting materials is an option. This method allows for creativity and customization but may not be suitable for producing multiple identical duplicates on a small budget.
- 3D Printing: With the advancement of technology, 3D printing has become an alternative method for creating miniatures. Hobbyists can use high-resolution 3D printers to fabricate custom parts or even print their own moulds. This option provides precision and the ability to create intricate designs.
When choosing the right casting material, consider factors such as cost, desired quantity, level of detail, and your skill level. While some materials like silicone and polyurethane are readily available and affordable, others might require professional assistance or specialized equipment for optimal results.
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Removing the cast from the mould
If you used a two-part mould, you will need to carefully separate the two halves before removing the cast. Ensure that the halves fit together tightly to avoid slippage and ruining the details of your cast. For a one-piece mould, simply remove the cast from the mould once it is fully cured.
To avoid damaging your mould or cast, it is important to take your time and be as gentle as possible during this process. If you encounter any resistance or difficulty, slowly roll the mould around to allow air bubbles to escape and facilitate the removal of the cast.
Additionally, it is recommended to use a mould release agent when working with silicone moulds. This will help ensure that the cast can be easily removed without sticking to the mould. With the right tools, techniques, and patience, you can successfully remove your plastic miniature from its mould and reveal your detailed creation.
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Painting and finishing techniques
Painting plastic miniatures is a detailed process that requires a number of steps to ensure a quality finish. Firstly, it is important to clean the miniature. This can be done with a craft knife, carefully removing any mold lines left behind by the casting process. Some people use specialised tools for this, but a simple craft knife held perpendicular to the edge of the miniature works well to gently scrape off the lines. If using a resin miniature, it is important to wash the model with warm water and soap before painting, as the releasing agent used in the mold can cause paint to chip off.
The next step is to assemble the miniature. Using plastic cement or super glue, the model should be fully assembled. This allows the painter to see any gaps or blemishes that need filling with putty. It also gives a better sense of the overall appearance and size of the model, and where the paint should go. Some people prefer to attach the miniature to its base at this stage, while others leave this until the end.
Now the miniature is ready for priming. Primers such as The Army Painter Matte White Primer or black primers can be used, depending on the desired finish. It is important to be aware of the distance you are spraying from, and the heat on the day of priming, as this can cause issues such as dusting.
Once primed, the miniature is ready for painting. Acrylic paints are most commonly used for miniatures as they dry quickly, are easy to work with, and do not require harsh chemicals for clean-up. It is important to use high-quality hobby-grade acrylics and to thin the paint with water if necessary. A variety of brush sizes are needed for different levels of detail. Stippling is a technique that can be used to add texture, highlights, lowlights, and reflections to the miniature. This involves building up semi-transparent layers of precisely placed dots.
If mistakes are made during painting, it is possible to go back over the area with the base colour and start again, or touch up the mistake if you are confident. Adding a lighter colour on top of the base colour can also add contrast to the miniature.
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Frequently asked questions
The traditional molding technique used for mass production is the creation of a Master Mold, from which a moulder will make a few "Masters". From these, a Production Mold is made, and the final product is cast.
There are several materials that can be used for casting plastic miniatures, including resin, plaster of Paris, and silicone.
To create a mold with silicone, first measure the width and height of the object, adding at least 1" to the width. Cut the sides and bottom piece to make a box that fits the item. Hot glue the item to the bottom piece and add the side panels with glue. Fill all gaps with hot glue to contain the silicone and pour equal parts of the silicone mixture into a container, mixing well.
To cast with resin, first prep your mold by spraying the inside with a mold release agent and wrapping it with tape. Mix the resin well and pour it into your mold, gently rolling the mold to let air bubbles escape. Repeat until the mold is filled and let it cure.
In most parts of the world, it is illegal to cast copies of miniatures without permission from the legal owner of the original intellectual property. It is important to be aware of copyright laws and intellectual property rights before casting miniatures.
