Pinholes in hollow wax

[Peter Angel]

Hello all.

I am attempting to make a hollow wax to give to a bronze foundry for casting.

I am pouring hot brown microcrystaline wax into a silicone rubber mold, letting it cool until it forms a skin and then pouring the warm wax out again.

However, I am getting tiny pinholes in my wax.

Any suggestions on how to prevent this?

Pete