Which Silicone Should You Use?

Silicone rubber is a top-quality and versatile mold making material that can be easily used to make different types of molds. It captures details well and is safe to use too. The molds turn out light, flexible, strong and resistant in nature.

When it comes to purchasing RTV silicone rubber, you have a choice of tin-cured and platinum-cured formulas. These two types of compounds use either tin or platinum metals to catalyze the silicone. The two silicones are widely divergent and largely incompatible with each other. Using the wrong one can result in a sticky mold or even end up spoiling the model.

Therefore, careful consideration of the following properties will ensure that you make the right choice Expansion joints .

Ease of use – Tin-based silicones are naturally more viscous and tend to pour easily. Platinum-based ones entail more accurate mixing and expert handling.

Barriers to curing – The curing of platinum-cured silicones is inhibited by the presence of sulfur in the model but the tin-cured variants can still be used on surfaces containing sulfur as long as the model is properly sealed. But these compounds require moisture for curing and excess humidity can accelerate the cure time. Platinum-cured silicones remain unaffected by humidity.

Shrinkage – A mold made of tin-cured silicone rubber is likely to shrink a bit as it cures while a platinum-cured silicone mold will continue to remain the same in size.

Resistance – Platinum-cured silicone is a tough compound that is resistant to heat; in fact it works better in high temperatures and can even be heat accelerated for faster curing. Tin-cured silicone molds cannot be expected to stay as durable when exposed to higher temperatures.

Mold life – Tin-cured rubber molds have a limited lifespan; they tend to lose their elasticity and break down or tear after a few years. In contrast, platinum-cured silicone rubber can last for decades, making it suitable for molds of valuable artifacts and other artworks.

Skin contact – Tin-based silicone should never be used on the skin whereas skin-safe variants of platinum-cured silicone rubber are available. In fact, platinum-cured formulas are offered in food safe versions too.

Cost – While all silicone rubbers are priced on the higher side, platinum-cured silicones are more expensive than the tin-cured ones.

Going by the above properties, it can be inferred that tin cured silicones are primarily suited for general mold making applications when the atmosphere is stable and the molds are not to be stored for long. They are especially appropriate for low-volume plaster casting, prototype applications and prosthetic works too.

Platinum cured silicones are not only durable and resistant but provide good dimensional stability too. This works well for specialized and high volume resin/epoxy casting, precision molding, special effects applications and encapsulations. Some variants can be used for making food or body molds also.

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