Guys, be very carefull using anything containing water when you are casting metals. you go and pour 1600 degree bronze into a mold with a little too much moisture in it and the steam can push it right back out the way it went in.
When I was in college I taught a class on metal casting and sculpture where we used the lost wax proccess to cast peices in bronze, silver, and gold.
We used a product that was similar to plaster but didnt retain moisture called casting investment you poured this around your wax model and put it all in a vaccum bell to remove all air bubbles that can cause your mold to crack when sudenly heated too. This was dried overnight and the next day while the metal was melting in the furnace you fired the mold in a kiln, this vaporizes the wax model and also removes all the water from the plaster like substance. You heated your mold up to 2000 degrees! when it hit 2000 you turned the kiln off and let it cool, for bronze your mold should be at 900 degrees when you pour your 1600 degree bronze in to get best results, shrinkage ect. The coolest part was removing the mold, when all red glow was gone from the mold you just dunk the who;e thing in a bucket of water and slosh it around, the plaster substance boils off and leaves you with whatever mold you carved in the wax...
I would be very careful using plaster of paris due to the amount of moisture still in the dried plaster, last thing you need is molten metal flying around...
One thing you could cast in plaster is casting pewter, I have seen molds made of masking tape used to cast a pewter ferrul around the tang of a knife, also designs cut in wood can be cast in the pewter, it only takes 600-700 degrees to melt it and you can use rather ordinary tools and such.
If you need any more info or ideas just email me and I will help you in any way I can..
Alan...
alanfolts@sprintmail.com
