Silicone mold life

[RAuser]

Have been pouring epoxy into tin cure silicone molds, and getting about 10 molds before the silicone starts to let go in the small features, less than about a half mm. If I try for 20 molds, pieces of mold about 1mm start letting go.

Anyone have basic recommendations for extending the number of molds?

[mangozac]

You're using pretty much the worst possible combination of materials! Try:

- Polyurethane resin (if possible)
- Platinum cure silicone
- Thick coating of release agent

Depending on the detail depth I work on an expected 30-40 pulls from a mould.

[RAuser]

Thanks. Have to stick with epoxy, but will try platinum molds, and a silicone agent.

Is heating good, to speed up the cure and demold, or is slower overnight cure better, for making the mold last longer?

[mangozac]

I would have thought that heat would be worse for the mould.

Also, have a look into silicone oils. I've heard of some people applying it to the mould and baking to rejuvenate the silicone, but have never tried it myself.

[RAuser]

Silicone oil is different from agent? I have silicone spray agent on the way, with the platinum.

I would like to find out about the heat. I don't degas, so when heating after pouring, the bubbles don't have time to pop.

[mangozac]

Yeah, silicone oil is different to silicone release agent. You only treat the mould with it occasionally, not every cast.

[Fleafa]

If you plan on painting, get wax release, not silicone release.

[RAuser]

No painting.

We've been using the silicone release and it has helped a lot. Spray the mold before each pour.