Lessons Learned: Soldering with Copper Solder Paste
So I got a delicious package of copper, brass, and silver patterned wire from Cool Tools a few weeks ago, and I've been looking at it, swooning over it, and playing with it every chance I've had since then. I mentioned awhile back that it had launched me into a ring-making frenzy; it also prompted me to (finally) try out the copper solder paste I bought months ago.
|Trying to solder this domed filigree heart was one of the hardest things I've ever tried to do! Too few points of contact plus solder that flows so fast plus fine meltable wires equals argh!|
I'd never used copper solder before, and I'd never used paste solder before–so it was a learning period all around. I learned to solder with Lexi using silver wire solder, and being the big fan of silver that I am, I've never needed to solder copper before now. But all of those cool patterned copper and brass wires begged to be made into rings, rings, and more rings, so off I went. I had no idea how different soldering copper would be. But first . . .
What is Solder?
Basically, solder is a material used to join two or more metal pieces (or two ends of one piece) together. Whether you use silver or copper solder, wire or paste, hard or medium or soft–all types of solder are alloys, and alloys are simply a blend or mixture of two or more metals. So solder is a metal alloy, sometimes with the addition of a binder (as in solder paste) and/or flux.
If solder is just basically an alloy, what makes metal solder different from, well, just metal? The binder and the flux, for one thing, but there's more than that. Here's a very basic but important point to remember: The right solder for a project is an alloy that melts at a lower temperature than the metal(s) being soldered. That makes sense, right? Because if it didn't, the metal(s) would melt, too, and you'd end up with a molten blob instead of jewelry (which is still possible, but let's hope we avoid it). Solder must also be able to adhere to the metal(s) being joined, so the metals in the solder have to be compatible in that sense with the metals you're soldering. For example, stainless steel is one metal that doesn't play so well with the others and is difficult to solder.
Soldering Copper with Copper Solder Paste
I think I would have had more early success at soldering with copper solder paste if I'd done a little more technical research about what copper solder paste actually is. In hindsight, thanks to some online research and a quick consultation about copper paste solder with Simple Soldering author and jewelry-making guru Kate Richbourg, here are some of my lessons learned.
As I said, I'd never used paste solder before, so it took a little trial and error to get the hang of it. In particular, I had to figure out how to use just enough–and by enough, I mean not too much. It takes less than I expected, and when I used the needle-like tips on the syringe, it was much easier to control the amount dispensed and to get a very fine line of solder.
And, as I said above, I'd never used copper solder before, either–wire or paste–so my experiments with it led to some good discoveries and reminders of things I'd already heard and learned about it. Most importantly, copper solder–at least this particular one–is not going to look like copper* when you're done. It will look less bright and shiny and silvery and different than if you'd used silver solder, and it's a fraction of the cost–both good reasons to use it, but it won't be copper colored. Copper solder paste contains mostly copper (about 95%) and some phosphorus** but also a bit of silver, too.
|Masterful Kate removes visible solder with a tapered barrel bur in a flex shaft.|
That little bit of silver is a small but mighty fighter, trust me; it will manage to get to the surface of all the copper in the solder and keep the seam from looking like copper (at least with the copper solder paste that I used). It won't be as obvious as if you'd used silver solder, but it will be there. Kate says she usually files away most of the join so the shiny silver part isn't very obvious. She uses a tapered barrel bur in her flex shaft to remove the excess solder and then refines the metal with finer files to remove the marks from the bur.
*My research tells me that there are "color match" copper solders available, so I'm ordering a selection of those and will be putting them to the test–watch this space!
**Phosphorus is the glowing element from which we get the term phosphorescence; it's also a flammable part of matches. This could explain why my copper solder paste literally, though momentarily, ignited (or maybe it was just the binder, or both). Remember to wear eye protection, avoid loose clothing, have proper ventilation, and keep a fire extinguisher on hand anytime you're working with a torch.
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