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Tin-Cure and Platinum-Cure Silicones


Silicone rubber is a material of choice for many mold makers and casting artists. The excellent flexibility, superior strength, enhanced resistance and long life work in its favor apart from the versatile usage for almost any application.

Silicone rubber comes as a two-part formula that can be poured, sprayed or brushed on the model/mold. 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 does not 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 details and can be made very quickly as well. Most materials – all types of resins, foams, wax and some low-melt metals – can easily be cast in silicone molds. It is also suitable for making soaps and candles, sculpture reproduction, cold casting. Special rubber variants can be used for making food molds, realistic masks, doll reborning, special effects and even life casting.

Types of silicone

Silicone rubber polymers come in two variations – platinum-cured and tin-cured. Both these types are very different from each other and are not even compatible with one another. Let’s find out how:

  • Tin cured silicone rubber uses tin salts (usually 5%) as a catalyst to initiate the cure from liquid state to solid. This is also known as condensation cure. Platinum cured rubber has a platinum catalyst (usually 10%) for curing and is also known as addition cure.
  • Tin cured silicones require moisture for proper curing and excess humidity can accelerate the cure time whereas humidity does not have any effect on the curing of platinum variants at all.
  • Tin cured variants are less expensive and also prove to be easier to use while platinum based ones turn out to be quite expensive.
  • Tin cured silicone molds and casts may tend to shrink a bit at times while the platinum cured counterparts enjoy virtually nil shrinkage.
  • Tin based silicone is tear resistant and even considered biodegradable. Its counterpart is considered very pliable and tough.
  • Platinum cure silicones offer exceptional heat resistance and work better in high temperatures than tin cure ones. The former can even be heat accelerated for faster curing.
  • Platinum cured silicones require very accurate and careful mixing, but this is not the case with tin cure ones.
  • Tin cured silicones are primarily suited for general silicone mold making, prototype applications and prosthetic works. 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 transparent versions also.

So, go ahead and make your silicone mold by all means, but do choose the type of silicone rubber with care.


Source by Ed McCormick

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