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Cleaning scrap gold


#1

Hello John!

Saw your post on cleaning up scrap. In addition I would add one idea
that was offered to me by a refinery worker. When you have the metal
molten, dash some saltpeter on the melt as you would casting flux.
Use your quartz or carbon rod and then flux normally and clean with a
rod again. A clean one if you have a second. If you have need for the
metal at present, there is no need to pour in water, really. You may
cast or pour an ingot now. After the metal is molten and the
saltpeter has been added and cleaned with a rod. Now add casting flux
to the molten button, let cool so it is no longer red. It is at that
point I’m told you have an amalgam. You then reheat, clean with a
rod, and use instead of going to a water pour; thus reducing a melt
on the metal.

If you can get some Zinc it is important to add back say a 1%
addition if you are using only scrap. It does need replenishment. Tim


#2

Hi Tim, Yes, I have heard of both the table salt and the salt peter
"fluxes" and they can help. As for pouring into water, I find it is
necessary because of the higher temperature needed to homogenize the
alloy is too high to cast at, that is, if you want the best possible
chance of a solid casting. Once the scrap alloy is (or newly mixed
alloy) is cooled you can cast at a significantly lower temp without
risking gas porosity or poor re-crystalization. It may not matter to
most folks especially on simple pieces but, when you are expecting to
work some metal arround an expensive stone it can make all the
difference. J.A. J.A.Henkel Co.,Inc. Moldmaking Casting & Finishing