Step 6: Bake the mold

Even though the plaster mold appears to be dry, there is moisture trapped in it. In order to dry it out and pre-heat it before melting the wax out use a conventional oven and very slowly increase the temperature. Heat shocking it will cause the mold to crack so be patient. Follow my next instructable on burning the wax out of the plaster mold for lost wax casting for further instruction. Have Fun!
Nice one! Check my instructable on making a vibration box to get the bubbles out! Thanks
one ever gnawing doubt.. it is said that plaster of paris is a bad mould material if u r casting anything with a higher melting point than of lead.. and disaster for silver or copper.. suggestions? <br />
Good question! I have casted silver and aluminum in plaster molds with great results. There is a particular method of doing this though: You have to heat treat your molds. For investment molds a conventional oven works well. Over several hours gradually increase temperature to 400 then gradually decrease to cool as to not crack your mold with temp shock. With lost wax without a vacuum chamber you'll have to get it much hotter to burn out the wax. I use a kiln and ever so gradually increase the temperature to 1000 degrees. Then gradually bring down to cool and leave in the kiln over night. It always works despite varying opinions. Good Luck!
<p>wouldn't it make more sense to cast, high temp metals while they are hot? to reduce the high gradient shock, then reduce the temp gradually? in a kiln with a programmable controller, designed for annealing glass. </p>
hey!! thanks for the tips! <br>will let u know next time i cast!
<p>I know this is two years late. Great Instructable. I have cast bronze and aluminum in a plaster lost wax mold. It's how I originally learned. I've done it for small (jewelry scale) sculptures and larger scale sculptures. The largest size is 18&quot;X18&quot;.</p>
Very informative! I just wish it was longer.
Wow. Thank you for this write up. I've been looking into doing this for some time (been using lost foam casting) and now this weekend I will try my hand in lost wax casting. Thank you again.

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