Re: Copper for casting


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Posted by Lyle Landstrom on July 10, 19100 at 11:43:15:

In Reply to: Copper for casting posted by Travis Larson on July 09, 19100 at 23:36:18:

I have made homemade brass by melting copper scrap and then adding zinc. I used old copper plumbing pipe for the copper which is melted first and then added zinc anodes obtained from a construction company as used for anodes on gas mains and steel bridges. Another source of zinc is from a galvanizer. The anodes work better because they are pure zinc and are in a golf ball size sphere which fits easily into the crucible. The galvenizer's ingot needed to be cut and was much too big to melt before cutting up.

This method produces alot of dross which needs to be skimmed and it's tough on a crucible as there's alot of scum formed on the inside walls but it does work.

One thing, when the zinc is added to the molten copper, flairing occurs and a greenish gas comes out of the top of the crucible. Do not breathe this gas. Do it only in a well ventilated area.

I have never tried pouring pure copper but the ancients did it so it is possible. I have heard that pure copper is pretty susceptable to air entrainment however.

There are a couple of chemical tests for identifying silicon bronze or maganese bronze from scrap. The manganese bronze test uses silver nitrate solution which turns dark grey instantly on manganese bronze. The silicon bronze test uses nitric acid which forms a precipitate when some of the metal is dissolved in it. maganese bronze is also slightly magnetic.

Both these metals are found at scrap yards and produce hardly any dross when melted (compaired to other copper alloys) and they can be melted over and over and mixed together. 90% of my copper alloy castings use either one of these metals obtained from a scrap yard about 1/4th the cost of a commercial ingot supplier. They can be mixed to produce whatever color you desire. You can use the same crucible for both. I'll probably get in trouble here by saying this but I've been doing it for years.

I have never made bronze by adding tin to copper. I would have tried it but finding pure tin in a good quantity is next to impossible. It is also more expensive than commerical bronze alloy so it is pointless to try to make.

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