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3d metalcasting test

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Thanks Matt but I meant in asking whether Tom was using a metal casting investment plaster or whether it was ordinary plaster of Paris.

tom osselton:
I'm just using ordinary plaster of paris although I did buy some high strenth plaster too but decided to try ordinary plaster first. The first thing I have to do is get it to dry out, it is still moist after being poured 22 hours ago. I have a kiln so I will do a meltout and slowly raise the temperature till it is dry after that they could be heated up over the furnace while the metal is melting.

The thing about plaster is that when it's "dry" there are still one molecule of water out of four that can detach it's self and generate steam. It should be heated in such a way as to get the entire piece up to 600 C and kept there to make sure it's cooked! Pour when hot. The sand should be silica sand. Plaster is plaster, additions in the form of sand or brick dust etc make it stronger. Ordinary plaster when completely dry will resist non ferrous temperatures.

Happy casting, regards, Matthew

tom osselton:
Thanks Matthew I'll keep that in mind, I know steam would be the main problem but it would not be hard to make a preheat chamber something say with a removable top so it could be poured on the spot. I have some fiberwool left over from my furnace build so it should not be a problem (fingers crossed)

Matt have you cast in plaster of Paris before?


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