Choosing the right silicone for the job.
While there are many different brands and styles of silicones, they all fall into one of 2 main categories: Condensation Cure Silicones and Addition Cure Silicones.
These two types of silicone are very different from one another and most importantly are not compatible with each other. Both polymer silicones need to be mixed with a relevant catalyst chemical to trigger curing from liquid to solid state, addition cured silicone requires a more accurate mix than condensation cured silicone.
Condensation Cured Silicones
First layers of silicone go over a carved piece. Crawford’s Casting 2013
Condensation cure silicones are the most commonly used silicones. They are relatively cheap, easy to use, and suitable for most applications.
Condensation cured silicone moulds cure with some shrinking making them great to capture fine intricate details. These silicones work great with polyester, epoxy, gypsum, wax, resin and plaster casting.
Condensation silicones use a tin-based catalyst.
Addition Cured Silicones
Chocolate mould- food grade silicone
Addition Cure silicones however are of a higher quality. Which means they last longer over time and multiple uses. Due to these factors they tend to cost quite a bit more than regular silicone – sometimes more than double!
Addition cure silicones are usually “skin safe” which means they are suitable for use against the skin in Life Casting.
Food grade moulds are also specifically made from addition cured silicone.
“Water clear” resins can only be cast into addition cured silicone, otherwise they don’t set properly.
Addition cured silicone is also known as “Platinum Cure Silicone” as this is the catalyst required.
For some more examples of the different types of moulds and silicones in action check out the gallery.