[gerald]

Bob Patrick told me that Flint Silica made a passable flux and was a little easier to clean up behind than borax. I bought a sack at a pottery supply place (@ $9 (US) for 50 #). The idea (I think) is to pitch it in the fire since it won't melt and run into the weld like borax does. I haven't been able to make it work, though, admittedly, I only tried it a few times. As Thomas Powers said earlier, borax is the thing unless you just want to try some of the other stuff.

BTW, if you decide to try some, get the coarsest grind you can find as large amounts of it floating around the shop can be unsafe to brethe.