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Is it safe to use a microwave for small aluminum melts? Answered

Seeing as how I have a spare microwave, and I've heard of people doing melts in a household microwave, I though that I'd try it myself.

What do I need to add so that I don't destroy the microwave?

"From a hardware store on Fourth Street, I bought a silicon carbide sharpening stone and 3 pounds of tin/silver plumber's solder; from Macy's, I purchased a microwave-safe casserole dish and a stainless-steel measuring cup; and at Williams-Sonoma, I found a cute cast-iron cornbread fish mold and a pair of long-cuff leather grilling gloves. " - PopSci's Theo Gray

A good source of silicon carbide? A better material? (I don't even understand its purpose here).

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jtobako (author)2007-04-21

Silicon Carbide will absorb microwaves and get hot-hot enough to melt some metals. It is used in SOME sharpening stones and in SOME crucibles (containers for melting metals). A jewelery supply, Budget Casting (home foundry supplier) or (occasionally) Harbor Freight (local cheep tool store) carry the crucibles, a hardware store would have the sharpening store (but make sure it says 'Silicon Carbide').

A combo of carbon/graphite and magnetite/rust will do the same. Read David Reid for more info.

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carbon (author)jtobako2007-04-21

So, basically, we have a cup of metal sitting on the sharpening stone, and that in turn sitting on something insulating but microwave-invisible? For the cup: Would it be alright to just use one made of stainless steel? For the insulator: Firebrick? Fiberglass insulation? Ceramic wool? Would any of these work?

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jtobako (author)carbon2007-04-21

The crucible works better because the heat is in better contact with the metal, but yes. Stainless works as a crucible, but keep an eye on it just to make sure. And make sure that there aren't any sharp edges for arcing to form on : ) Insulating firebrick (the lightweight stuff, you can scratch/cut it easily) or ceramic wool work, fiberglass might start melting-not sure of the heat resistance and temp that the silicon carbide is going to get to.

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