Quote Originally Posted by desbromilow View Post
why does the welder go over the joint with a second pass? is it to smooth the bead, or some other reason?
Lead gets a film of oxidation very quickly just like aluminum. If you noticed his routine, he would heat dab and back away. The rapid heating was melting the base metal from within under the layer of oxidation the dabbing while the heat was there and adding the filler material while pushing through the oxidation even though you may not have seen it. this joined the two layers but might not have made a watertight bond Since the layer of oxidation was more or less burned away now. going back over the bead would allow a nice even fluid flow.

I used to use lead as a body filler on cars instead of the resin and hardener. Just needed a coarse grind to the metal or file it with a body file. use a lead stick and a torch heat the metal rub the stick over the surface to what was called tinning. Then melt and fill if you got too much you could heat and smooth out with a wooden paddle or file it off an remelt the filings to recover the excess lead you had used when making shapes if you needed more lead later you had to get rid of the oxidation by filing or spot heating and forcing the stick thought the layer then go back over and smooth with a paddle.