Silicone rubber is a material of choice for many mold makers and casting artists. Excellent flexibility, superior strength, improved strength and long life work in your favor, plus versatile use for almost any application.
Silicone rubber comes as a two-part formula that can be poured, sprayed, or brushed onto the model/mould. In fact, it is safe and can be used for both mold making and casting, as long as it suits your application. Another benefit is that silicone doesn’t stick to anything, so a release agent is mostly not required.
Silicone rubber is often used for general mold making applications as the molds manage to capture fine detail and can be made very quickly as well. Most materials (all types of resins, foams, wax, and some low melting metals) can be easily poured into silicone molds. It is also suitable for soap and candle making, sculpture reproduction, cold casting. Special rubber variants can be used to make food molds, realistic masks, doll revivals, special effects, and even life molds.
types of silicon
Silicone rubber polymers come in two variations: platinum-cured and tin-cured. Both types are very different from each other and are not even compatible with each other. Let’s find out how:
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Tin-cured silicone rubber uses tin salts (typically 5%) as a catalyst to initiate cure from liquid to solid. This is also known as condensation curing. Platinum cured rubber has a platinum catalyst (usually 10%) for curing and is also known as addition curing.
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Tin-cured silicones require moisture for proper cure, and excess moisture can speed up cure time, whereas moisture has no effect on the cure of platinum variants.
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The tin-cured variants are less expensive and also easier to use, while the platinum-based ones are quite expensive.
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Tin-cured silicone molds and models can tend to shrink a bit at times, while platinum-cured counterparts enjoy virtually zero shrinkage.
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Tin-based silicone is tear resistant and is even considered biodegradable. Its counterpart is considered very foldable and strong.
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Platinum-cure silicones offer exceptional heat resistance and perform better at high temperatures than tin-cure silicones. The former can even be heat accelerated for faster curing.
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Platinum-cured silicones require very precise and careful mixing, but this is not the case with tin-cured ones.
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Tin-cured silicones are primarily suitable for general silicone mold making, prototyping applications, and prosthetic work. Platinum-cured silicones provide good dimensional stability and work well for precision molding, special effects applications, encapsulations, and paints. The latter comes in food-safe, skin-safe, and clear versions too.
So go ahead and make your silicone mold by all means, but choose the type of silicone rubber carefully.