Edwin Wise

Casting a Thigh

Last tuesday I spent my evening molding a thigh. Not the entire leg. Not the calf. But a thigh. I'll be creating skin and muscles based on this mold, to be wrapped around a skeleton, to be used as a vivisection of our poor actor.

This is the first time I cast a thigh, and the results are very good. Though there are quite a few "bubbles" in the mold (I used the thick silicon, applied in a bit of a hurry) I will sculpt these out of the clay positive I'm making this weekend.

I made the cast from just below the actor's knee to up into the short hairs at his hip.

Think about it carefully. Notice the delicate hairs on the inner thigh.

Sure, we lubed up his fur with the approved materials; he did an excellent job of that, far above average I thought.

Sure, silicon doesn't *stick* to anything. Sure.

It does get a good, firm, mechanical hold, though. I know this from personal experience. I have thick hair arm and I did test patches on myself when I got the stuff. It tugs a fair bit, but the hairs pull
free of the silicon.

For my thick, coarse hairs at least.

Mat, the actor, has fine hair.

Had.

There are apparently several factors involved in how much a mold sticks to the model's hair.

There is, of course, the fact of lubrication or lack thereof. I used petroleum jelly for the areas where plaster was applied, and a silicon release for the other spots.

There is the mold material. Alginate binds hairs, but it is weak and lets go easily enough. Silicon binds hairs and is stronger -- so a good greasing is necessary. Plaster really sticks good, and is totally inflexible, so you better be diligent there.

I'm thinking that a soft silicon detail layer (like a thinned slow-set Body Double) will release hairs better then the fairly hard and thick fast-set Body Double. I didn't do that this time.

All of the above factors I kept in mind. There was one more, however, that I didn't think about.

The type of hair itself.

Thick straight hair release easily.

Thin, fine, and (probably) curly hair is more likely to bind in the mold. In this case, you may be safest using alginate or a very soft silicon in a detail layer.

The problem with any hair in a mold is that it creates flaws in the mold. Your best bet may be to just shave the darn model and be done with it.

PS: I enabled comments, disabled comments, and just no re-enabled comments. I keep vacillating on this point -- user comments versus the annoyance of blog spam.

The scale has tipped, at least for now, towards allowing comments.

However, I also put a pox on all those who would put spam into personal blogs. May the fleas of a thousand camels infest their armpits; may all of their beverages be salty; may all of the dogs in their neighborhood crap on their lawn; may goats invade their yard and eat all of their bushes. So say I.

Posted by Edwin at May 12, 2005 02:56 PM