I have bought about 200 pounds of soft lead through Rotometals. I got it when it was much cheaper than it is now. This is the purest lead I have ever seen. When you first melt it down to make ingots you will get the blue, green, gold oxides build up on top. If you mix in about 1000 grains of hard lead shot per 10 pounds of pure it will homogenize the melt. I am told a little tin will do it too. If you don't add the shot or tin you can literally skim this ultra pure lead to nothing. The first time I did it I thought man I got to get this junk out of this lead. I screwed up and skimmed it off and lost a lot of lead, but I did go back and reclaim it later.
I started to add the lead shot and bingo no more loss of this lead due to the oxides. The hardness increase is not even measurable at the rate I gave. It will literally only homogenize the melt. It will also flow better. Ron