Resin casting question

[Regnir]

I've been experimenting with a technique that I've heard mentioned but never found very concrete information on and I've run into a small issue with it.

I've been using Smooth-on OOMOO RTV to create single-part moulds to create things like walls, scenic bases, and small flat features like landmines. I've read about "capping" the mould after pouring resin into it to ensure that the un-detailed side of the resin object is perfectly flat, using things like a sheet of glass treated with a release agent.

I pour the resin and then have a few sheets of 1/4"(nice and heavy) of glass that I set on top of the mould, laying it down at an angle.

The problem I have is that after laying the glass cap onto the mould slowly, I always end up with a sizable bubble on the flat side of the resin piece. It's not a huge deal most of the time, but some of the bubbles have been pretty large.

If anyone has experience with this sort of thing, I'd love some advice to correct my issue.

Thank you!

[Johnnycrash]

Over fill the mold just a little bit. Then cap.

[Regnir]

Hmm thanks. Perhaps I just wasn't overfilling it quite enough.

I'll give another set a shot tonight, thanks again.