Copper can contaminate welds, and will. Someone check ont he zinc content in NS as the zinc will burn at a very low temp, and you cna see this as a green flame from the molten metal. Zinc in a gas form is deadly poisonous, so if you do try melting anything with zinc in it I suggest that you do it outside.
The furnace I described previously can be outfitted with a propane burner, and you can find some info on it at
www.backyardmetalcasting.com . This kid is sharp and has good links to others who have built propane burners for their furnaces.
If your propane burner will heat your forge to welding temps then it will heat more than hot enough to cast with. The lindsay books link I left has some books on propane furnacce burners as well.
I have seen someone post links to dealers in casting materials as well as the supplies to line the furnace.
I am using some of the clay sand mix I used for the furnace liner for sand casting, but have heard that you can use plaster of paris to make molds in as well. I think you have to cook it off first to drive the water out of it, and preheat it before the pour. Plaster is cheap though and for experimentation it should be the ticket. If you can carve it in wood, you can cast it in metal.
www.ray-vin.com has some interesting information about casting in several types of media, and mold making techniques.
Pendative, I caught your post and will answer it tonight. Most of my information is on my home box. Will help out any way I can.
Doc
