Mixed Metals: Tips for How to Solder Copper to Silver and More
Lexi’s fun mixed-metal hearts in copper, brass, and silver.
Copper has had a rough reputation when it comes to soldering. Sure, plumbers have been soldering it for decades, but the esthetics of soldering copper plumbing and a seamless joint are not a consideration, whereas we usually want extremely clean solder joins in our jewelry. Many jewelry artists think this is close to impossible. Not so.
Mixed metals at their finest, David Huang’s copper vessel features gold-lined copper patina with a sterling ring on the edge.
Soldering Copper: Keep It Clean
The whole trick to being able to solder copper well is that with copper and its alloys, cleanliness is probably the most important rule. Copper, brass, and bronze have been repeatedly called "nasty metals," and that name is well earned. They oxidize rapidly when the torch is just touched to the metal, and it happens very quickly. It’s important that your metal is clean of any residue and fingerprints. Always scrub your metal clean with Dawn detergent and a green kitchen scrubber, with wet-or-dry sandpaper, or 9-micron 3M finishing film. If your metal is textured, scrub with a brass brush, soap, and pumice, making sure you get in all those little crevices of texture. It is important that the water sheets off the copper.
Soldering Copper: Flux, Flux, Flux
Another huge tip is to use Prip’s flux, available from most jewelry-supply stores. This specially formulated pinkish liquid flux is a godsend when soldering copper. Purchase a small empty spray bottle, fill it with the flux, and keep it on your bench just for copper soldering. After you clean your metal, spray a thin coat on the metal and let it dry; then spray on another thin coat and begin to heat your piece with the torch. If you are doing a bezel, be sure the bezel has been sprayed, also. Crank up the heat a bit and work fairly fast, because the longer you dawdle, the quicker the oxides will build up and the flux will burn off, no longer protecting the metal.
Lexi’s student Darcel Shelman solders copper onto silver.
Silver Solder on Copper?
I’ll answer one of the most asked questions readers write: Yes, I use silver solder and silver bezel on everything copper. Copper solder and copper bezel both oxidize rapidly and can create a real mess, so I use easy solder almost exclusively on all my copper work. Extra easy will work, too. (The reason we don't use extra easy on silver is because it leaves a yellowish line, which will show up a few weeks after soldering, unless you patina the piece.) If your soldering is neat, you will never see that silver line of solder. If a silver bezel on a piece of copper bothers you, then throw a nail or a piece of binding wire into a small cup of pickle; it will copperplate your bezel and also copperplate any offending solder.
Lexi’s silver Shaman figure with an etched copper overlay.
Soldering a Copper Overlay
If you’re doing an overlay, it works well to sweat-solder the back of the top piece (meaning to melt some solder on the back of the top piece) and then pickle. Scrub it with Dawn and a scrubber, and then lay it onto the backplate, but remember to spray some Prip’s flux between the layers. Then spray a coating of Prip’s flux over the entire piece. Crank up the torch and go in really fast.
When doing an overlay in copper and sterling silver, it may be easier to solder silver onto copper as you are practicing. Copper has a higher melting point (1,984°F) than silver has at 1,640°F. If you are soldering copper onto sterling silver, you may overheat the sterling and the copper will sink into it. It can be done quite successfully, but watch for the softening of the silver; if it starts to look molten, pull back with the torch and let it cool before going back in.
Example of sweat soldering
Now go get some copper, take a deep breath, and solder something. So what if it melts (and it will take a lot of heat!). Just breathe. It’s only metal. Have fun! —Lexi
To learn more about soldering from Lexi, check out her second new soldering video, Metalsmith Essentials: How to Solder Jewelry Vol. 2. Pre-order the DVD, or, if you can’t wait (who can blame you?), download it instantly (also in HD).