What Casting Material Can Be Cast Into Silicone Rubber Molding Material?

There are many different types of casting material available to suit many different types of projects. If you are creative with jewellery then you may wish to look at the various resins for casting unique resin jewellery pieces. 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. Plaster is the most ideal casting material for this purpose. Every project has its own requirements and we will look at the most popular casting materials and their uses in this article.


Plaster is a versatile, cheap and safe casting material to use for many different types of applications. This material only requires a latex mould and not the more expensive silicone rubber molding materials which are generally needed for resin or pewter castings.

There are several types of plaster and each one is best suited to a particular application. Try to stay away from the Plaster of Paris types as the surface of the casting won’t retain much detail and it has a low surface hardness.

Casting Plaster types are best suited for general purpose plaster casting such as for children’s plaster painting ornaments. Casting plasters have a harder surface which prevents chipping and provides a good surface for painting.

For projects that require a harder and more durable plaster casting material you might want to look at one of the stone plasters. These are more expensive but the strength is superior.


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 Resin: The most common type of opaque resin in use today is polyurethane two part resin. This comes in many forms and various setting times. The time it takes to set hard when mixed in most cases is very short, usually 3 – 5 minutes. This resin gets really hot and it is recommended to use a Silicone Rubber Molding Material.

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 castings can be painted, drilled and sanded.

Transparent resins: The cheapest clear casting material is polyester resin. This requires the addition of a toxic chemical called MEKP to create the chemical reaction which hardens the resin. Special care needs to be taken when using this material and gloves should be worn.

Polyester clear casting resins produce a very clear and hard casting which can be polished by hand to produce glass like effects. 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.

Resin Jewellery makers have really taken to this type of resin. The only drawback is that larger block castings cannot be made. We are talking about castings larger than your fist and polyester is still preferred for castings of larger size.


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 moulds are needed for this type of casting and there are special high temperature silicone rubber molding materials.

There are many varieties of low lead and leadless alloys to choose from and melting pots are good gloves are recommended.


More and more people today are using moulds to cast concrete items for their gardens or for their own business. Plastic or polyurethane rubber moulds are the most commonly used and are generally more durable.

Special concrete mixes have been developed to get a finer surface finish but even a ready mix bag available at any hardware store can be used with good results. The type of aggregate used is also important in getting a good surface finish. Don’t forget that once the casting is removed from the mould it needs at least a good week to fully set and needs to be kept wet to allow the chemical reactions to take place and prevent cracking.


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.

Post time: 04-30-2017