[George777]

Silicone rubber that vulcanizes at room temperature is very expensive. Has anyone had experience with fillers mixed into the silicone to bulk up the pour when making rubber molds. I've tried old ground up cured silicone rubber mixed into virgin silicone rubber and it seemed to work okay. I was wondering if cheap recycled rubber from tires etc. would work.

[awerby]

Those rubbers often contain a lot of sulphur, which poisons silicone rubber and keeps it from setting properly. Some (like the platinum-cure types) are extremely touchy about this sort of thing, and even touching them with a rubber glove will cause cure failures. So if you plan to do this, try a test first, and only use it on a real project if the test is successful.

Andrew Werby
www.computersculpture.com

Silicone rubber that vulcanizes at room temperature is very expensive. Has anyone had experience with fillers mixed into the silicone to bulk up the pour when making rubber molds. I've tried old ground up cured silicone rubber mixed into virgin silicone rubber and it seemed to work okay. I was wondering if cheap recycled rubber from tires etc. would work.

[George777]

That's a good point about the Sulphur, I didn't consider whether sulphur would be in other rubbers. I'll have to consider a more chemically neutral filler.

[Tristar500]

I've used polystyrene beads from an old bean bag chair with good sucess.