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What Casting Material can be cast into Silicone Rubber Molding Material?

Every project is different and there is a casting material to suit each of them. Jewellery creators for example may want to look at the various casting resins for interesting effects. If you are after a fun and creative party activity for children then you may want to investigate the casting of plaster ornaments and plaques for them to paint. Simple casting plaster is the most ideal casting material for this purpose. Every project is different and requires a specific casting solution and we will investigate this further in this article.

PLASTERS

Plaster is a versatile, cheap and safe casting material to use for many different types of applications. This material can be cast into almost all types of moulds and doesn't require expensive silicone moulds to be made.

There are many types of plaster and each are suited to a specific task. Plaster of Paris is probably the least suitable for most casting applications as the surface hardness is low and detail is not defined.

Casting Plaster types are best suited for general purpose plaster casting such as for children's plaster painting ornaments. This type of plaster has a harder surface to help prevent chipping.

Stone plasters are also available for those projects that require more strength and a harder surface. These plasters have superior strength but are more expensive.

RESINS

There are many types of resin. They generally made up of either polyester, epoxy or polyurethane and can come in either clear or opaque finishes. We will look at the various types of clear and opaque resins and their applications.

Opaque Resins: Polyurethane resin is the most common type used today. There are various products available with different setting times and hardnesses. The time it takes to set hard when mixed in most cases is very short, usually 3 - 5 minutes. When the resin is setting the temperature can be very high and the use of silicone rubber molding materials are recommended.

This type of resin can be coloured but the base colour which can range from white to creamy beige needs to be factored in to any colour mixing. Special polyurethane pigments can be mixed into part A before mixing in part B.

These types of resins are not as brittle as clear polyester resin and are therefore suitable for making model parts and small detailed items. The finished castings can be sanded, drilled and painted.

Transparent resins: The cheapest clear casting material is polyester resin. This type of resin requires the addition of MEKP to allow it to harden and this chemical is quite toxic. Gloves should be worn when using this casting material and a well ventilated are is essential.

These resins produce a hard and water clear casting which can be hand polished to produce glass like finishes. This product is excellent for embedding and due to the slow setting times it allows most bubbles time to rise to the surface.

Another type of transparent resin which is really starting to become popular is the epoxy type. These resins are much easier to mix at a ratio of usually 1 to 1 and have low odour. They are also a lot less toxic than polyester resins.

Epoxy resin has become quite popular with jewellery makers. One limitation of epoxy resin however is that larger castings can become problematic when setting. If the casting is larger than a fist then polyester is recommended.

METAL ALLOYS

Pewter casting is a popular hobby and people use low melt metals to create a wide range of model parts, toy soldiers badges and even jewellery. Special high temperature silicone rubber molding materials are needed when casting these metals.

A melting pot and a good set of gloves are recommended.

CONCRETE AND CEMENT

More and more people today are using moulds to cast concrete items for their gardens or for their own business. The most common types of moulds used with concrete are made from either durable ABS plastic or polyurethane rubbers.

Ready mix bags of concrete are ideal for the beginner to start casting and the more advanced caster can experiment with special finer concrete mixes which produce smoother and finer surfaces. The type of aggregate used is also important in getting a good surface finish. When the concrete has set in the mould and removed it needs at least a week to fully cure and during this time needs to be kept wet to prevent cracking.

CONCLUSION

These are just a few of the many casting material possibilities. We haven't gone into additives which can enhance the materials mentioned above such as metal powders which can be added to transparent resins to make metal like cold casts. Before embarking on your casting project and mould making it is important to do you research and even talk to an expert. They can direct you onto the right path before you purchase any expensive mould making and casting material.

 

About the Author

Stan Alderson has been in the hobby ceramic field for over 25 years and has accumulated a gold mine of knowledge in many fields including mould making and casting. Read more about Casting Materials and mould making techniques on our website.

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