I have been casting with straight Clip On WW lead and having good results. Every time I flux, all I have is a thin layer of black scum to remove, It amounts to very little.
Yesterday, I melted 10 pounds of lead ingots in the casting pot and added about 1/2 pound of Monotype to see what the results would be. The whole thing was melted at about 650 and I fluxed. I had a layer of silver slush on top about 1/4 inch thick that had to be removed.
Could it be that the Type was contaminated with Zinc? I don't think that I had it hot enough to melt the Zinc, but could Zinc go to slush at that temp?
Or, could that have been Tin and Antimony coming to the top? I removed the slush and started casting and the boolits were just fine.
Thanks