Casting aluminum giudance

I’m nowhere near any kind of experience level of doing casting but are you pulling a vacuum on the plaster of paris before you pour it. I’ve seen videos of that done to where they pull a vacuum to get rid of the excess air pockets.

Hi TBJK,

I have done it but I didn’t notice a difference. I think there is a steep temperature gradient between the outside and the inside of the mold.

Did you manage it like you wanted? If not I can try to show you how I would do the sprues tomorrow. I someone will help make some crucible tongs I can do a grand can smelting/lost foam lesson sometime this break.

No aluminum in the jewelry casting equipment. It’ll cause severe pitting on silver and other metals with contamination

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Hello there, If I was casting this part. I would cast it upside down. I would print it using wax printer. I don’t know how to use the wax printer, OR I would make the part out of another material and cast silicone rubber around it to make an exact duplicate out of wax. Then we incase the wax in plaster because of your shape, I’d have the legs exposed out of the top of the plaster i.e. cast it with the legs as shown pouring plaster around the base and up until it fills the cup part. The entire thing can then be heated to allow the wax to melt out leaving your empty mold. We can flip the heated mold, pour in aluminum. Hope this gives some kind of idea.

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Are you heating the PoP to drive off the water prior to the pour? Or at some other stage in the prep/for some other reason?

Hey Rashon I really like your idea. The mold is too bulky and the legs are deep inside the mold. I think your approach would make it easier for the wax to melt away because it is not deep inside the mold. I’ll give it a try.

I left the molds inside an oven at 300F for about a day. But after opening them I saw that the wax mold had not melt completely.

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If using plaster of Paris to do lost wax or foam casting you must heat the entire wax and investment enough to dry the plaster of Paris and drive off any contained water. After that you must heat it enough to melt the wax, then increase the temperature enough to actually burn out the wax still clinging to the plaster. After that you must further increase the temperature to above the temperature at which your metal melts to weaken the plaster, then allow it to cool down to just below the melting temperature of your metal. You can’t do all of these steps at once. It will probably take about a day to go through the whole temperature range. If you heat the plaster too quickly it will crack from the steam escaping too quickly. The high temperature at the end of the cycle weakens the plaster so that it will help fall apart after you have cast. Allowing it to cool to just below the melting temp of the metal allows the molten metal to flow completely into the mold before it solidifies. You also must do all of this without letting the plaster cool back to room temperature or the plaster will absorb moisture and you have to do it all over again. After pouring the metal into the mold you wait a short time for it to solidify, then drop the mold into a bucket of water. The steam from the water soaking into the hot plaster will soften the plaster and it should easily fall apart when prodded to leave only your metal casting.

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