And Im at a loss as this happened 3 times so Im asking you smart and lovely people. The casting was 1/8" think and ripped in half when I opened.īased on Andrew Martins formula (calculate the cubic volume for water and x3 for the amount of plaster) and my results I'm thinking this formula is broken in some way. I came back 7 hours later to open the mold. I waited 2 hours and checked the casting, it was still too soft so I held off opening the mold. I let it sit for 15 minutes then drained. My plaster is hard after 12 minutes.Īfter a week of drying I wet the mold and poured slip. It pours and sets into the piece I'm casting but mounds at the end. I've found that the consistency of the plaster is think, like lightly whipped whipping cream. I mix with a drill/paint mixer for 3 minutes. I sift my plaster into the water and let it slake for 3 minutes. I'm Canadian so I want this in metric and converted it. Ive attached am image of a calculator I made in Sheets but my ratio is 2.25 Quarts H20: 6.75lb(Andrew Martin formula).
I am using a NEW bag of #1 pottery plaster. I've attempted to convert the formula several times now and I'm feeling pretty silly as I cant seem to get the results I'm looking for. Ive read Andrew Martin's Mold making and slip casting book but I refuse to use his plaster formula which uses metric, imperial, volume, AND weight. My troubles mostly have to do with mixing the plaster. Ive been working on creating some slip casting molds and I've had some mixed results.
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