Lessons Learned: Soldering with Copper Solder Paste
I never used copper solder or soldering paste before, so it was a learning period all around. I learned to solder with Lexi using silver wire solder. Being a big fan of silver, I 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 before we get into the nitty gritty of copper soldering, let’s go over a few basics for beginners.
What is Solder?
Solder is a material used to join two or more metal pieces, or two ends of one piece, together. All types of solder are alloys—no matter if you use silver or copper solder, wire or paste, hard, medium or soft. Alloys are a blend of two or more metals. Solder is a metal alloy, sometimes with the addition of a binder (as in solder paste) or flux.
If solder is an alloy, what makes metal solder different from just metal? The binder and flux, for one thing, but there’s more than that. Here’s a basic but important point: The best solder for a project is an alloy that melts at a lower temperature than the metal(s) being soldered. That makes sense, right? After all, if the alloy melted at a higher temperature than the metal you’re soldering, the metal would melt, too. You’d end up with a molten blob instead of jewelry, which is still possible, but let’s avoid it.
Also, solder must adhere to the metal(s) being joined. The metals in the solder must be compatible with the metals you’re soldering. For example, stainless steel is one metal that doesn’t play well with others and is difficult to solder. You may want to avoid that combination and stick to metals that can be soldered more easily.
Soldering Copper with Copper Solder PasteI wasn’t expecting copper soldering paste to be so different. If I had conducted more research about what copper solder paste actually is, I would’ve been more successful. In hindsight, I learned from research and consulting with Simple Soldering‘s author, Kate Richbourg about copper paste solder.
I never used paste solder before, so it took a little trial and error to get the hang of it. In particular, learning the amount of the solder was tough to figure out. It takes less than I expected. When I used the needle-like tips on the syringe, it was much easier to control the dispensed amount to get a fine line of solder. That turned out to be the perfect amount! Once I had the hang of it, I was pleased with the results.
And, I never used copper solder before either (wire or paste), so my experiments with it led to good discoveries. Most importantly, copper solder is not going to look like copper* when you’re done. It won’t look as bright, shiny and silvery compared to using silver solder. These are both good reasons to use it, but it won’t be copper-colored. Copper solder paste contains mostly copper (about 95 percent), some phosphorus**, and silver, too.That little bit of silver is a small but mighty fighter, trust me. It will get to the surface of all the copper in the solder and keep the seam from looking like copper. 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 as obvious. She uses a tapered barrel bur in her flex shaft to remove the excess solder. Then, she refines the metal with finer files to remove the marks from the bur.
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*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 for updates!
**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 momentarily ignited, or maybe it was 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.