I believe that knowing the theory and properties behind materials used is crucial in problem-solving, which is why I have decided to write this blog on silicone in the context of prosthetic making.
The most common silicone used in prosthetic making is a platinum silicone. It is an addition cure silicone, which means two parts are mixed together (typically in a 1:1 ratio although this depends on the product) which will then start a catalyzation reaction which hardens the material. As this is a catalytic reaction, the silicone is sensitive to heat, which means that on a hotter day, the silicone’s working time is shortened as the heat accelerates the reaction. Subsequently, this also means that the colder the ambient temperature, the slower the catalytic reaction.
Platinum silicone or the Plat Gel series most commonly comes in 00, 10 and 25, which represent the shore hardness of the silicone (the higher the number the harder it is). These silicones can be altered with additives to change the properties of the silicone, such as lengthening the working time or changing the viscosity (thickness) of the silicone. For example, retarder is used to slow down the cure and lengthen the working time, deadener and softener are used to soften the silicone, hardener is used to harden it, thixotropic is used to thicken it and silicone oil is used to make the silicone oily and act as an intrinsic release agent. As these are additives in a catalytic reaction, they can also affect how long the silicone takes to cure or other properties. To add something into the silicone, it’s referred to as intrinsic. This means if I were to mix pigment into the silicone mix, I am intrinsically colouring the prosthetic. In comparison, if I were to add colour on top of the prosthetic, like when applying makeup, this would be referred to as extrinsically colouring the silicone.
Many things can inhibit the cure of silicone, such as sulfur and latex, which is why it's important to use sulfur-free clays and disposable mixing equipment when working with silicone.
Silicone can be used for making flat moulds, two part moulds, brush on moulds etc, as well as of course being used to make the prosthetics themselves, inluding other applications such as animatronics and medical prosthetesis. Current leading industry professionals are even investigating the uses of silicone in 3D printing!
Knowing the products and materials you use I believe is important, as it helps you to understand why it's used for different applications and contexts, as well as to troubleshoot when an incident occurs.
