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Can I use plaster-of-paris as a mold material for making an aluminum casting?

I do not have access to any proper mold making materials, only items that can be found in a hardware store or a pharmacy. I would like to know if I can use plaster of paris as a mold material for a simple pour type casting using a lost wax type method. Any help will be greatly appreciated.

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rickharris10 months ago

http://www.anvilfire.com/iForge/tutor/vi_copper_c1...

reasonable tutorial. I like the use of the plant pot to cook out the wax.

https://www.youtube.com/results?search_query=simpl...

lots of you tube videos.

rickharris8 years ago
Must be totally dry - and Pour the aluminium into a very hot mould. After the metal has set drop the whole thing in a bucket of water to breakup the plaster. Ware safety equipment - hot metal and damp WILL explode in your face.

So, how do I make it totally dry, and how hot?

Allow to air dry for several days after casting the plaster, before pouring heat up to 200 deg F or more to avoid cooling the aluminium and to ensure it is totally dry.

Use all sensible safety precautions, do this over sand in case you spill some molten aluminium.

http://www.lestercast.co.uk/investmentcasting.asp?...

I poured the PoP last night, and plan to wait until tomorrow to even start trying to melt out the plastic. My biggest question is how do I dry it completely w/o harming it? Also, I don't have an oven, only a propane grill, which only goes up to about 500 degrees (more than most ovens though) so would that work, and if so, would I just start on low and slowly increase the temp? It's my first time casting with PoP (2nd time ever, as lost foam didn't work) so I'm really in need of step by step for the plaster mold prep to be as safe as I can be.

amosojas2 years ago

Can I use plaster of Paris to build a kiln of heat capacity of 800°c - 1200°c? Can it withstand the heat capacity?

No

heathbar647 years ago
I've read alot about casting, but not actually tried it yet. From my reading, I understand that once the plaster sets, you put it in the oven for a while to make sure it is totally dry.

How long at what temp?

Oddly enough I bought a five dollar gallon plaster of paris bucket and it works great for me. I heat it up and put zinc in it. Heck I even napalmed it and it stayed still.
There's a problem with the 'dry' comment. Cured plaster of Paris is a hydrate. That is, the reason it remains hard is water trapped in the crystal structure. If you heat it past 300'F, the water will be released and the plaster will turn back into a clod of powder. (Aluminum melts around 1200'F.)
lemonie8 years ago
I have done lead-castings with Polyfilla (and I'm panning on doing some more). Make sure it's dry, if there's moisture left in there you'll have problems with steam. But yes, dry plaster should do it - but have a spill-tray or something else underneath in case the mould breaks, or your hand slips.

L
mbudde8 years ago
Yes, I do believe that you can. Thats what they use in this instructable. https://www.instructables.com/id/Building-a-furnace-creating-molds-and-casting-je/