I know about clip on zinc wheelweights, but I did not know about stick on zinc wheelweights. Somehow it never occurred to me. It should have.
I have been separating and saving my stick on wheelweights for 3 years and I had about 10 gallons of them. I do not have a muzzle loading firearm so I did not have a use for them until I decided to try a 50/50 mix of stick on wheelweights and clip on wheelweights. So I started melting my stick on wheelweights into ingots. My mistake was using two propane torches to melt the stick on wheelweights faster. I must have melted some zinc stick on wheelweights. I got all the signs of zinc contamination, but I did not recognize it because I had never had it occur previously. There was a mushy metal floating on the melted lead alloy. It was impossible to flux the alloy properly. When pouring metal out of the dipper onto the surface of the lead, it turned frothy. Bullets did not fill out well. When the lead level got low, the alloy turned purple. The most frustrating part was the spout freeze even at 850 degrees F. I would unclog the spout by heading it with a propane torch. That worked, but even better was to put a drill bit (held by vice grips) up the spout and turn it slightly. This always worked, but I could not keep the spout from clogging. Finally I realized what was going wrong. I decided to throw away the 40 pounds of zinc contaminated lead alloy. The bullet moulds cleaned normally. I cleaned out the electric furnace. There was a glob of metal on the end of the rod which closes off the bottom pour spout. I pulled that off with pliers. Now I know to set the electric furnace on 700 degrees F. and do NOT use the propane torches. I posted a photo of the zinc stick on wheelweights. All the weights in the bottom row have "Zn" in the upper right hand corner. The other weights do not. Yes I checked all of them with a magnetic and these are not magnetic. I can sort out the magnetic and zinc wheelweights before melting, but with the furnace set on 700 degrees F. and not using a propane torch, I do not have to worry about making a mistake.