Saturday, July 4, 2015

09 Plaster Production Molds Nº 229




I left this coddle board off so it would be easier to soap the plaster. Click on any image to enlarge it.



I use a 50/50 solution of liquid soap and water as a parting agent. I pour the soap from a glass jar into a small container when I apply it. That way, the main soap solution doesn't get polluted. I am using an old paint brush to apply the soap. After each application of the solution, the plaster soaks up the soapy water. I keep applying the soap solution until the plaster stops absorbing it. Evidently, the soapy solution and the plaster create a barrier that doesn't let new plaster stick to the old plaster.




Once the plaster has been soaped, I place the last coddle board in place and secure it with C or G clamps. I also seal around the bottom of the coddle with coils of oil clay pressed into place. I press coils along all the vertical seams as well.






I figured out that I would need about 6 pounds of water and 9 pounds of plaster. I measured out 6 pounds of water and put it in my mixing bucket. While I was measuring out 9 pounds of plaster I changed my mind and went with 7.5 pounds of plaster instead. So before I mixed the plaster and water, I removed 1 pound of water. My final ratio of water to plaster was 5 pounds of water to 7.5 pounds of plaster.



I use clean cold water. Cold water inhibits the setup of the plaster. I add the dry plaster to the water, sifting it rapidly and evenly into the water through my fingers. Then I let it slack for a few minutes until all the plaster is wet. If I do not agitate it, the plaster will not start to setup for awhile. Once the plaster has soaked up the water, I push the island of plaster down below the surface and I squeeze all the lumps out of it, stirring it as I squeeze the lumps. The more the plaster is agitated, the faster it will start to setup. When I can draw an S in the surface of the plaster and it leaves the trail, it is ready to pour. I turn ON the mold table vibrator, then pour the plaster into the coddles in an even, steady stream.

I turn OFF the mold table vibrator. I wash my hands, tools, and mixing bucket in the bucket of water I have ready for that purpose. If there is any excess plaster, it gets scraped into the lined trash can. Never put plaster (dry, set, or wet) down the drain pipes. I always let the plaster set up for at least ONE hour.




Before I left the mold to set up, I checked to see if there were any leaks. Here is a small one. It plugged itself.






There was another small leak inside, behind the oil clay build-up. It also plugged itself up. There is just one more mold piece to make for the lower torso.






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