i am a novice at mold making and casting. i have moved to a larger model to cast and am having trouble calculating how much mold material to use for the volume of my box. i am using c&r loo mold material 50/50 plaster/silica. i miscalculated how much volume i would need and the thing hardened before i could make more to fill up to the level my wax required.
thanks, josie
volume calculation
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Bert Weiss
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Many people, (Anna Boothe teaches this technique) build large pate de verre molds in seperate sections or rings. If you want to try it with the partial mold that you already have you only need to do a couple of things:
Leave the poured mold around the wax and in the box.
Carve a couple of notches or keys into the top of the plaster/silica that you have already poured. People often use coins to carve out neat bowls for this. These keys will lock the two pieces of the mold together so that they don't shift latterally.
Paint a release on the top of poured plaster. Vaseline, clay slip, etc.
Pour more plaster/silica on top to complete the mold.
The two mold sections will come apart. They must be steamed out and cleaned up and reassembled to accept the glass. Often people will cover the entire exterior of the two pieces with another layer of plaster/silica, sometimes using wire in addition, to strengthen the mold.
Anna Boothe uses this system to build very tall pieces. She will start with the bottom ring, pack it with glass, add another ring, pack that with glass and so on. This way she can get specific colors where she wants them. The seams mean that there is inevitably going to be some cold working.
As for measuring volumes, I like to pour rice into odd shaped molds and measure its volume.
ch
Leave the poured mold around the wax and in the box.
Carve a couple of notches or keys into the top of the plaster/silica that you have already poured. People often use coins to carve out neat bowls for this. These keys will lock the two pieces of the mold together so that they don't shift latterally.
Paint a release on the top of poured plaster. Vaseline, clay slip, etc.
Pour more plaster/silica on top to complete the mold.
The two mold sections will come apart. They must be steamed out and cleaned up and reassembled to accept the glass. Often people will cover the entire exterior of the two pieces with another layer of plaster/silica, sometimes using wire in addition, to strengthen the mold.
Anna Boothe uses this system to build very tall pieces. She will start with the bottom ring, pack it with glass, add another ring, pack that with glass and so on. This way she can get specific colors where she wants them. The seams mean that there is inevitably going to be some cold working.
As for measuring volumes, I like to pour rice into odd shaped molds and measure its volume.
ch
volume calculation
thanks so much. i had missed the volume calculation on the bullseye tip sheet.
josie
josie