Hi,

I have recently tried to make several moulds using silicone rubber and whilst the overall results are pretty good I am having some issues with bubbles within the mould, as well as sticky patches which I believe is due to incomplete mixing of the two parts. Does anyone have any advice for effectively mixing the two parts together as well as good practice for avoiding bubbles in the final part? I have access to a degassing system but am having problems degassing anything more than 100g quantities due to spilling of the silicone (I assume a larger container will help), and even in small quantities bubbles still exist.

Thanks

Jamie 

Silicone always expands to several times its original volume so a bigger container is needed. Proper degassing should remove almost all of your  bubbles.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks for your advice. Definitely something I will try.

Do you have any thoughts on the mixing? Is hand mixing enough, particularly for larger quantities?

Thanks

Jamie

Hand mixing is fine.  Mechanical mixing has the danger of aerating the silicone a lot making the degassing a much longer task.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

The best way to avoid unmixed material is to use the double cup method - mix the batch initially in one cup for 2 minutes, and when you think it is totally mixed pour it into a second, clean cup, and mix for another 2 minutes.