What's the best way to make a mold from a clay sculpture?

Question

I love sculpting on self-hardening clay; most of my sculpts are irregular pieces like busts and full figures(mostly fantasy figs). I found out though that the clay is fragile and a bit too heavy. I would like to cast them in plaster of paris but I can't think of a good medium. Also, will the "foam" dentists use to make a cast of teeth work?

Answer 1

Hey, another one doing fantasy figs. :) What size do you work in? Since you're working with clay I assume it's larger than the 28mm I work in.

The traditional method of creating moulds from a clay master is to embed it in plaster and then either split the mould (which should be prepared for this) or wash out the clay. But I don't think you want to do that. Unless your work is really big.

Another method would be to create latex moulds. With plaster backing if it should prove necessary. You can cast plaster into this. Or resin.

If you're working at my size then it's best to go for silicone rubber moulds and cast in resin or pewter.

For the techniques: I've just posted a bunch of link with mouldmaking info over here:
http://answers.yahoo.com/question/index;_ylt=Aj_phVgfnfldib_I4NaRIGfsy6IX;_ylv=3?qid=20071010221308AA24zGB&show=7#profile-info-AA11154556

As to the foam, I don't know it but it would probably work. I'm guessing it will also be very expensive. The material I know for this is kneadable silicone rubber. You mix up two components and these will cure into a mould. Kind of like this stuff:
http://www.townsendatelier.com/store/knead_a_mold.php Also fairly expensive.

By the way, you can also have a look at that site since they have several materails for drawing moulds from figures.

Another option would be to sculpt in another material. For larger figures (up to 30cm or so?) polymer clays like FIMO are popular. Cores can be made of instance aluminium foil to save cost.
I'm using epoxy putties which is very strong. But it's also fairly expensive, so it's more for small stuff.

Answer 2

Casting Clay Sculpture

Answer 3

A damp towel will work. I prefer to use a spray bottle filled with tap water. Give the piece a once over spray. Wait 5 or 10 minutes check it and spray it again. Watch not to get it too wet. keep checking and giving it a light spray about every 10 or 15 minutes I have made the mistake many times and this will get it back in a workable state I normally use high fire stoneware

Answer 4

This store carries all kinds of modeling compounds, for just the need you have.
http://www.dickbkick.com
You'll have to do some searching when you get there.