Building up silicone mold question

[scorpia777]

Hello!
First timer using silicone to make a mask mold and was wondering if I can use Type I silicone caulk over a A+B silicone detail coat. I plan on doing two coats or so with the A+B and build up thickness with the caulk. I know silicone usually sticks to silicone but was wondering if the different formulations will be problematic. Trying to get some experince in and don't want to waste the good stuff while I'm learning.

 

[udog]

Hi
The main problem I see is that silicone caulk shrinks a lot, that can give you weird issues as you are combining two diferent shrinkage rates (platinum´s negligible).
My opinion is no, don´t do it. If you have already spent money in that A+B silicone (I assume it´s platinum), at the end your mold will be a mix of good silicone and cheapo caulk. Caulk by the way, has properties (tear strength, stretchiness, contraction etc.) that are far bellow addition (platinum) and condensation (tin) silicones´ properties.
You might end throwing away the money you spent. Besdes, I wouldn´t be so sure about adhesion between different silicones (or even the same) once they´re fully cured. And not sure if it´s a good idea to put on caulk over delicate plat silicone when it is finishing it´s curing process.
Doesn´t sound as a good idea to me.

 

[scorpia777]

Thank you very much for the reply and insight. That is exactly the kind of info I wanted. I hadn't even considered the shrinkage issues. Thanks again.