Resin, shellac and plaster help

[Wellss01]

I am taking a plaster casting form a byvac vac forming ( no problems there). I want to use this plaster buck as a vac forming tool to make more. Is there anything i can coat on the plaster to make it a bit more durable. My thoughts were either shellac or possibly polyester resin as i have heaps. Any suggestions or ideas would be much appriciated. Im hoping start forming early next week or soon after



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[Propsjonnyb]

The problem with plaster molds for vac-forming is they need drilling, to allow the suction to pull the softened plastic, down onto the mold , plaster if a bit fragile, which is why most use wooden 'plugs' as you can drill almost all the holes you need without damaging the plug. Resin might be your best bet as you should be able to drill this out. Plaster is ok, if the mold is small say three to five inches , if its too big you won't get sufficent suction to form the plastic roud your mold and that in essence is the problem.