On 2013-05-13 8:57 PM, IVP wrote:
> I'm guessing you'd need to let it cure properly so the hot metal
> doesn't heat any remaining free water and crack the mold

This is a well-known procedure. I'm not inventing any new methods. After
the plaster hardens, it is to be baked in an oven for a few hours to get
out as much water as possible. Then it's safe to pour liquid aluminum
into it. But I'll be heating the mold with the blow torch before doing
anything with the aluminum to make sure it's free of water as an extra
precaution.

I'll be melting outside, on a solid concrete slab, with the mold inside
a hole of a cinder block.

If it feels unsafe, I'll dig a hole in the ground, line it with gravel
and use coal instead of a blow torch so I don't have to be near the
aluminum while it's melting into the mold. Cover with a concrete slab
with a hole to breathe and let it sit until the coal burns out. Doesn't
get any safer than that.

Aluminum melts at low temperatures, and this method has been used to
cast alloys of much higher temperature.

If it really becomes an issue melting the aluminum safely, I'll just use
zinc and melt it under a candle or something outside, and stay far away
so as not to breathe any fumes (zinc fumes are toxic).

But the volume of metal I'm dealing with is so incredibly small that I
very highly doubt that I'll run into any issue safely casting it.

I just made the plaster mold and it turned out much better than I
expected, even after creating too thick of a mix. The precision of the
plaster getting into all the notches of the gear is incredible.

--=20
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