Sunday, August 08, 2010


Still trying not to be discouraged from all the recent major setbacks in shooting - it's only going so well.

Anyway, I thought I'd throw a couple photos of the recent prosthetic disasters up for you to see. This is actually the kind of info I wish I could have found online when I started doing all this a couple years ago. I've mentioned before that everyone says foam latex can go wrong a million different ways, but no one ever really explains it. So, I'm going to explain a few way to understand what went wrong with your foam latex.
This here is an unbaked piece. I didn't see any point since I knew it was no good. It was pretty difficult to pry the mold apart because the latex was still gelled as well as it could be, so it wasn't a solid, but a sort of solid.

And here's the result of finally pulling it out of the negative mold. I wish I could say I meant it to look like this, but it in no way resembles the original piece. And I wish I could say it was usable even like this, but it's garbage. Very freaky looking garbage, mind you - gives me some ideas actually.

Here's a closeup of a baked piece that didn't turn out. Normally the pieces should have a uniform consistency throughout, so what it looks like on the surface should be exactly what it looks like inside. This happened because only the outside skin of the piece gelled. Sort of like skin on pudding or something, but a little thicker. It gels from the outside in, not consistently.

When you bake a prosthetic that hasn't fulled gelled, the inside becomes a crumbly mess, the whole piece has no elasticity and rips very easily. How do you tell if it's fully gelled before baking? The best way is by seeing what's left in the bowl, or leave a blob sitting out. If you poke it and you can very obviously feel it's still squishy inside - it's not cured. You should be able to press it and have it feel like a uniform consistency all the way through. And remember, it takes a little longer for it to fully gel inside the mold.

From my experience, it doesn't really matter how long you leave the filled mold out either. No one every really explained that. I wasn't sure at first if there was a window of time from totally gelling that it had to be baked. I've left pieces out for a day or so before baking and it seemed to have turned out just as well as the ones from the same batch that were baked right away. So if you're not sure, just wait a bit longer before you throw it in the oven.

Most instructions will tell you all about adjusting for humidity and how it results in the ammonia in the latex being whipped off faster because the gelling agent is more active at higher temps. That's something you just have to work out on your own. Cut back on the gelling agent and cut back on the de-ammoniate time until it works - sounds fine, but be prepared to waste a lot of latex getting it right.

In my case I was dealing with 75% humidity - I had no idea where the safe range was for cutting back on either part of the run schedule. Took awhile, but I more or less sorted it out - still trying to fine tune it so I can accurately gauge it.

Anyway, that's it. This is an example of one way it can go wrong, and now you know what it actually looks like and what caused the problem. I've run into other problems over the past couple years, I'll probably run into them again. When I do, I'll make sure to document it.

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