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I am thinking of a way to make a slumped "finger labyrinth" bowl or platter. My idea is to use silicone caulk to laydown a bead for the labyrinth. Then to frame around it and cast it in Plaster/Alumina mix. Then use this as a mold to slump into the labyrinth. Sound plausable? Ideas for a release agent? Thanks

If you're doing it in silicone caulk you won't need a release agent as long as you don't create undercuts. The silicone is flexible enough to be eased out of the mold. I'd do it on something like an 1/8 inch acrylic sheet, though, with some kind of release. You probably don't need it--I remove plaster molds from acrylic sheet simply by flexing them off the sheet--but it's not a bad idea to be on the safe side.

Apply your caulk to the sheet, let it cure, then build your dam with clay. You can spray a light coat of lacquer on the clay to seal it then add your plaster mix. Let the plaster cure for at least a few hours before you pull it off the silicone.

If your silicone design is very intricate, so that there's a danger of the design locking into the plaster and possibly breaking it when you remove it, cover your acrylic sheet with smoothed-out aluminum foil. Do everything on the foil, then when it's time to remove the silicone from your mold, unfasten the foil first. Then flip the mold over and use the foil to finesse teh silicone out of the crevices.

Thanks cynthia