Q: Which is best for soldering precious metals, the liquid self-pickling flux or the white paste kind?
A: The self-pickling fluxes, such as Batterns, are designed primarily for typical commercial work in gold. For the jeweler soldering heads onto a gold ring, Batterns is a fine flux to use. The principal attributes of the stuff is that it’s an active enough flux to allow solder flow, but not extremely active, so it won’t burn off too quickly on gold work, while at the same time (and this is the key to the stuff) not promoting excessive fire scale at the solder joint.
The white paste fluxes, such as Dandix and Handy flux, are much more active fluxes, and promote solder flow much better, but tend to actually promote fire scale formation around the joint as they work and burn off. Batterns won’t leave you with a gold ring and white gold heads with a bunch of hard to polish blackish crap in the crevices around the head as readily as will the white paste fluxes. Mind you, if you over-heat the piece, it will still do it.
With silver, though, Batterns is a waste of time. It’s not designed for that use, despite what the bottle says. And with copper or brass? Not a chance. For these metals, of course, it’s not an important issue, as the fire scale doesn’t penetrate the surface, but stays at the surface where it’s easy to pickle off. However, even with copper and brass, Pripps flux (which is described in a separate article) or the paste fluxes will help reduce the work. But many jewelers happily use Batterns for gold work with no problems.
My own preference is still for the white paste fluxes. Our local supplier (C.R. Hills, Detroit) sells a dry powdered version of this flux which I find very convenient—just add water. I only mix up about a thimbleful at a time in a shot glass, which lasts for the day’s work. That way I always have nice creamy clean flux to use instead of the other brands where the whole jar gets lumpy and dried out and full of bits of this and that. Keeping the flux clean is a part of keeping the joints clean and getting good seams.
However, these paste fluxes have one disadvantage. There’s a good deal of material there; the paste is thick and can get in the way. Thus, work with tiny details can be harder to do with the paste fluxes. So my bottle of Batterns is still there. I use it now and then for chain repairs, delicate retipping work (on the white gold it’s a little friendlier sometimes) and when working with platinum, although platinum doesn’t actually need any flux. Still, a trace of Batterns can be useful to stick a solder pillion in place until it’s hot enough to adhere on its own.
by Peter W. Rowe M.F.A., G.G.