Wednesday, April 9, 2014
09 Plaster Production Molds Nº 21
Today I poured the mold piece for the sole of the right carving wax foot. Preparation is a key to anxiety-free plaster mold making. I have a half-filled 5-gallon bucket of water, and a lined trash container ready ahead of time. The bucket of water is used to rinse plaster off my hands, tools, and mixing bowls. The trash container gets the excess plaster left over from the pour. NEVER put plaster, (dry, set, or wet) down the drain pipes. Click on any image to enlarge it.
I apply a soap parting agent to the plaster build-up and the carving wax foot. I have already described this procedure in previous posts.
I prepare the coddles by marking how high I want to pour the plaster with masking tape. I also roll out some coils of oil-clay to seal around the bottom of the coddles.
I place the coddles around the plaster build-up, and clamp them securely. I try to get the walls of the coddles as square as I can to the molding table. Then I press the prepared oil-clay coils around the bottom of the coddles to seal them. These coils also help keep the coddles in place when I turn on the vibrator.
I use a yogurt container to bring clean fresh water to be weighed. For this mold piece, I am using a ratio of 1.50 pounds of water to 2.25 pounds of plaster. That gives me a consistency of 67.
I weight the plaster on the scale.
I quickly sift the plaster evenly into the water. Always add plaster to water. I let the plaster slack. Once the plaster has slacked, I push the island of plaster down into the mixing bowl and I squish the lumps out with my fingers. I mix the plaster until it is smooth and creamy.
I turn on the vibrator.
I pour the mixed plaster into the coddles. When it reaches the masking tape markers, I stop pouring. I gently pat the top of the pour to release air bubbles that have risen to the surface. I turn off the vibrator.
I pour the excess plaster into the trash container, then I wash my hands and the mixing bowl in the water. NEVER put plaster (dry, wet, or set) down the drain pipes.
I leave the mold to set up for at least an hour. I usually just walk away from the mold, turn out the lights, and leave it until the next day. During setup, the mold will get hot. Then it will cool down. I am not in a rush. I know what happens, so I can wait until tomorrow.
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