On 2013-05-14, at 11:29 AM, "Allen Mulvey" wrote: > We did this in college foundry work for investment casting. > We mixed talc in with the plaster to make it easier to > calcine (drive off the water). If I recall properly, each > molecule of gypsum tends to retain two molecules of water so > by reducing the gypsum (plaster) content you can reduce the > bonded water significantly. I don't remember the proportions > we used. Experiment a bit. You just need enough plaster to > hold it all together. Preheat the mold before pouring. Correct, it's a dihydrate=85..but can be made into an anhydrous form with e= nough heat. -m --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .