Factoid
07-27-2009, 03:56 PM
This past weekend I finished up a brush-on silicone rubber mold of a small statue. I think the mold turned out pretty well, but I won't know for sure until I cut it off the master.
Before I do that, though, I need to make a mother mold so that the rubber holds it shape during casting.
My plan is to make a 3 or 4 layer thick mother mold of plaster-gauze wrap. Just dunk in water and apply in layers. I know plaster wrap won't be very strong, though, and might have a tendency to crack. Anyone worked with this stuff before and know how it holds up under weight?
I'll need to be able to flip the mold upside down, fill it with mold materials and then remove the shell without the thing breaking.
Do I need to reinforce it to prevent against breaking or does the guaze do a good job of that already? I was thinking of adding something like tin foil or wire mesh between layers (specifically window screening or chicken/garden wire).
The mold I'm working on would fit inside a 20" tall cylinder about 6 inches in diameter, so I don't have a ton of surface area to cover or support, but I might use some heavy materials for casting in the future, such as ice or concrete.
Also before applying the plaster wrap to the silicone mold I was thinking about putting down a layer of something water resistant so that I didn't have to worry about getting the plaster wet. Could I wrap the inner mold in plastic-wrap and then apply the plaster mother mold around that? Then I'd do the same with the outer layer after it set and seal the whole thing with packing tape or something for a good seal. My reasoning here is that eventually I want to use this mold to make an ice sculpture but I'm concerned that gravity will force a small amount of water through the cut-seam of the silicone inner mold and contact the plaster, which would weaken it.
Before I do that, though, I need to make a mother mold so that the rubber holds it shape during casting.
My plan is to make a 3 or 4 layer thick mother mold of plaster-gauze wrap. Just dunk in water and apply in layers. I know plaster wrap won't be very strong, though, and might have a tendency to crack. Anyone worked with this stuff before and know how it holds up under weight?
I'll need to be able to flip the mold upside down, fill it with mold materials and then remove the shell without the thing breaking.
Do I need to reinforce it to prevent against breaking or does the guaze do a good job of that already? I was thinking of adding something like tin foil or wire mesh between layers (specifically window screening or chicken/garden wire).
The mold I'm working on would fit inside a 20" tall cylinder about 6 inches in diameter, so I don't have a ton of surface area to cover or support, but I might use some heavy materials for casting in the future, such as ice or concrete.
Also before applying the plaster wrap to the silicone mold I was thinking about putting down a layer of something water resistant so that I didn't have to worry about getting the plaster wet. Could I wrap the inner mold in plastic-wrap and then apply the plaster mother mold around that? Then I'd do the same with the outer layer after it set and seal the whole thing with packing tape or something for a good seal. My reasoning here is that eventually I want to use this mold to make an ice sculpture but I'm concerned that gravity will force a small amount of water through the cut-seam of the silicone inner mold and contact the plaster, which would weaken it.