I want to say that the alum foundry I programmed for used potatoes for a
degasser. I do know that they put the potatoes in their melts for something.

wrote in message
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flux and degasser

Two cheap tips for aluminum casting:

(1) Use canning or rock salt as a flux when melting. It will float on
top of the melt protecting the aluminum and if the charge is salvage
metal it seems to cause the contaminates to separate so these can be
skimmed or sink to the bottom. Learned this from watching an aluminum
salvage operation.

(2) For degasser, fill a piece of ½ inch black iron pipe about 4
inches long with swimming pool chlorine powder. (much cheaper than the
tablets). Use a wad of aluminum foil or brown paper in each end of the
pipe to keep the powder in. Use tongs to plunge the pipe to the bottom
of your crucible and stir it around. Be careful not to breath the
fumes!

If you are getting porosity in your castings, check the pigs/ingots
that you pour when the molds are full. If these are sound most likely
the metal is too hot.

Try painting the bottom and sides of your foam patterns with water
glass (solution of sodium silicate) and let dry. Use plaster or sand
to support the coated foam pattern. I can get very smooth surfaces
this way.