So,I've been using my mask molds for a while now.i started with a latex mask from a kid's hallowe'en costume,then started ordering from the Internet,then makin my own.here are a few observations:

I don't use mixes that tend to the drier side.Mine are wet,almost sloppy;I do this to get into all the nooks and crannies(what's a cranny?).I'paint"the molds first with a cement/colour and I vibrate them upon completion(generators are REALLY good for that!).My voids are few to non-existent.I've had some of these pieces out in the weather for a couple of years,and they show no deterioration.

I have latex,silicone,urethane and plastic molds.I do NOT like plastic that I have tried so far as they are broken too easily.I was eaven backing them with foam during the pouring process(gotta cram the mud in!)and the thinner walled molds(and these come from a large supplier of same)are thrashed.

Urethane?Love it.Takes abuse,cleans up nice and has just the right flexibility;these will last a while.

Silicone?Easy to make and easy to work with.

Latex.Has to be backed with sand or some such,like fibreglass.

I also use stainless bowls-Boy,can they take abuse!!

I know that others out there have used molds longer than I and may disagree with my findings.But,what the hey,I'm still having fun!!

Cheers from here