When things go wrong at the bench, it is almost always one or more of the four f’s: flame, flux, fit, and, um, fastidiousness. OK, cleanliness, but that doesn’t start with f, and four f’s sounds a lot better than 3 f’s and a c.
• Flame means the amount of heat. Most people are reluctant to use enough flame, early on anyway. I like to recommend that people melt some things on purpose, and watch closely. It really helps to give you a sense of what the stages are leading up to total collapse, and that helps you know when to BACK OFF. But really, not enough heat is more often a problem than not enough. Sure, you won’t melt anything if you’re cautious—including your solder! Plus, firescale is more about the time you spend heating than the temperature. When you heat too cautiously, you exhaust your flux and—ta da!—firescale. So, keep the torch moving, keep it away from corners and other parts that stick out, but go in hot and get the job done.
• Flux is a funny problem. People have different favorites, even though they’re doing the same thing—soldering and preventing firescale. Some people use a “firecoat”, then add a “soldering flux” in the seam. So, you might coat your whole piece with boric acid suspended in alcohol, flame the alcohol off, and place a drop of Prip’s flux, or Cupronil, or My T Flux right in the seam.
I tend to coat everything with the same thing, unless the soldering goddess isn’t happy that day, and then I figure, “She doesn’t like that one today, maybe She’ll like this one, or a couple different ones”.
My favorite flux is Magic Flame mixed with alcohol. I did a quasi-scientific test a few years ago. I soldered matching sterling bezel cups (which were really scrap from my perspective—I would never actually use them in a piece) to sterling rectangles with hard solder. I used each of a bunch of fluxes I had, including Firescoff, MyTFlux, Cupronil, Batterns, Handi Flux and Magic Flame, plus boric acid and alcohol. For the water-based fluxes, I applied with spray bottles onto heated surfaces so they coated well. Then I pickled thoroughly, gave them a light sanding, and checked how much of the surface was covered with firescale.
By the way, the best way to do that is to stand the piece vertically on a piece of white paper. In the white reflection, firescale shows up clearly.
I expected the Firescoff to be the best. It costs a LOT, and it coats really well on a hot surface. It comes in a really great spray bottle.
In my test, Magic Flame had almost no firescale. Handi Flux was the absolute worst. All the others were closely grouped, with about ¼-1/3 of the surface firescaled. Go figure. But your results may be very different, because soldering styles vary a lot.
Even with the high cost of Firescoff and of silver, this test is one I encourage to do yoursellf. Buy several fluxes—it’s just not that much money. Do a piece with hard solder to test each one, and compare. See what works best for you.
• Fit—well, if you’ve been reading this blog, you know I’m a nut for fit. I like seams to disappear after solder and clean-up, so they have to fit. I even like to do marriage of metals.
A couple of unfinished marriage of metals pieces
Here’s a tip I find very useful when filing ring shanks or bezel strips—anything that will be filed while straight, then bent to make a seam. It’s hard to tell whether these filed areas will fit together nice and snug until you bend them, then it’s tough to re-file because they aren’t straight any more.
No dark line between the silver and the reflection means it's flat
So, after you file and before you bend, hold the filed surface flush against something reflective that you know is flat, like a steel block. Recently, I even used my iPod Touch for this. If it lies flat and flush, you’ll know it’s filed right. If it rocks, or you see a shadow along part of the filed edge, do it again.
If you’ve already bent, say, a ring shank, and it almost fits together, but not quite—that’s when you use the sawing-through-the-seam trick I wrote about in a previous post.
• Last comes fastidiousness (cleanliness). I don’t have any tricks for that. Clean is clean. I will say, if you have just filed, the seam area is clean—just don’t touch it with your fingers. Don’t let anti-flux (like ochre) get in your flux. If you take too long trying to solder and it isn’t working, pickle for a good while, rinse, and try again. If you can’t get all the discoloration to pickle off, try this—give the piece
a heavy coating of flux, especially one of the “self-pickling” fluxes like Battern’s or Griffith’s—heat until the flux becomes glassy, and pickle it again.
You maybe don’t mean to mind your p’s and q’s, but you can never neglect the 4 f’s. OK, OK, 3 f’s and a c.
{ 2 comments… read them below or add one }
Thanks for the very specific advice and problemsolving tips. Generalities don’t go very far when I’m in the middle of a project.
Some good tips. Cheers.