I like making dichroic glass cabochons, and they look really good when they are accented with sterling mounts. Since I’d disconnected my lampwork torch to do the demo, when I got back into the studio I decided to hook up my jeweler’s torch and work on some bezel mounts.
There are a lot of options when choosing a torch for jewelry soldering, and I was tempted to buy the same Prest-o-lite torch we used in my jewelry class, but it requires acetylene for fuel. Since I already have propane and oxygen for my glass working torch, I chose to keep things simple and bought the Smith Little Torch, a lightweight little handheld torch which comes with 5 tips.
A bezel consists of two parts, the ring around the stone (or glass), and a back plate. For my silver bezels I’m using 22 gauge sterling sheet for the back plate, and the bezel ring is made from 26 gauge bezel wire, which is flat or patterned fine silver wire. It’s best to use fine (99.99%) silver, because it’s much softer than sterling, which makes it a lot easier to fit around the stone, and to burnish over the stone to hold it in place. The bezel wire should be about 2/3 the height of the cabochon, ie 4mm for a 6mm thick cab.
Making the bezel ring
1) Measure the circumference of the cabochon, with wire, tape or the bezel wire itself.
2) Transfer that measurement to the bezel wire, adding a little (maybe 1/2 mm) for an easier fit. You want the fit to be close enough to allow you to burnish the bezel metal down to hold the stone, but not so tight that you chip or crack the stone when you fit it into the bezel.
3) Cut the bezel wire to length and file the ends square. The cut should be a right angle to the long edge of the wire, and the face of the cut should be filed to a right angle to the surface.
4) Bend the strip into a circle, taking care not to warp the strip, and make sure the ends meet without any light showing. This is where the right angles make everything easier. File and adjust until you get a perfect fit, which will ensure a good solder joint.
5) Cut small (less than 1mm) chips (pallions) of hard silver solder, and place one on a soldering board or charcoal block. Flux the inside and outside surfaces of the ring around the joint, and then place it on the pallion, so that the seam is perfectly centered over the chip. You can see the pasty flux and the solder chip at the 6 o’clock position under the ring in the photo below. A little solder goes a long way: this bezel ring is 4mm wide (tall), and the chip of solder is almost too large.
6) Light your torch, and gently heat the work, concentrating on the block around the ring and avoiding the bezel wire (it will melt in seconds). Watch the flux: it will boil, and then dry and turn white, and then turn clear and glassy. Once it reaches the glassy state move the flame closer to the block, still avoiding the bezel itself.
7) Keep moving the torch and watch the solder chip. Once it reaches melting temperature the ring will drop down onto the block and the shiny solder will flow up along the seam. Congratulations, you’ve finished the first step! Drop the ring into a crockpot of pickle to remove the oxidation and burned flux.
Soldering the ring to the back plate
1) The next step is to cut out the back plate, using a jewelers saw or shears. I prefer to use a saw, because shears will distort the plate, and it’s much easier to solder the bezel ring on a flat surface. Just cut a square or rectangle larger than the stone, you can trim to shape later.
2) The surface needs to be clean, and the best way to ensure that is to sand it on a sheet of 400 grit wet/dry sandpaper. Once you’ve sanded (I do both sides) handle the piece only by the edges.
3) Once the ring is clean (a uniform white-silver color), pluck it out with copper or wooden tongs (don’t use ordinary tweezers or you’ll contaminate your pickle) and drop it in a baking soda solution to neutralize the pickle.
4) Rinse and dry the ring and then shape it to fit the stone, without warping it vertically. For round stones it’s easiest to shape it on mandrel made for the purpose, but if the stone you’re mounting is irregular or has sharp corners you may need to use pliers to carefully adjust it to fit. The important thing is to keep the walls of the bezel vertical, so that the stone can drop straight into the ring once you have it shaped. If it’s too snug turn it over and try the other side. The goal is to shape the ring so that it drops down over the stone without any pressure. Once you get a good fit mark it with a pencil or pen so that you know which side faces down.
5) To ensure a tight fit between the ring and the plate, put the ring bottom edge down on your wet/dry sandpaper and sand it with light pressure from your finger[s]. Turn it 90 degrees and sand again, and repeat until you’ve sanded in all four directions. Then drop the ring on your clean back plate, hold it in front of a light or window and make sure you can’t see light between ring and plate. Repeat until you can see no light.
6) Cut 3 or 4 pallions of hard solder (I use wire solder, but sheet solder is fine), light your torch and direct the flame on each chip, melting each into a little ball. Balls work better for the next step.
7) Place the back plate on your soldering brick (I describe another approach* below), and brush flux over the surface. Drop the bezel ring onto the plate (sanded side down) and use fine tweezers to place a few little balls of solder inside the ring, right in the angle between the back plate and the wall of the ring. Again, a little solder goes a long way: I use 2 balls about .5mm in diameter for a ring 10-12mm in diameter. If you use too much it will form blobs that might interfere with placing the stone, or you’ll have to grind or sand them away. Here’s a bunch of rings and plates before soldering.
8) Soldering the ring to the plate is done the same way you soldered the ring seam, using primarily indirect heat. Move the flame around the ring, heating the back plate, and watch for the transitions of the flux. Keep an eye on the solder balls, and put any of them back in place if they move as the flux boils. Once the solder melts you’ll see a bright line of solder run around the seam between the ring and the plate.
In soldering bezels (soldering in general) it pays to remember that you can use too much heat. If you heat the ring too much it will melt. If you’re heating the piece and the solder won’t melt, stop and clean everything, check the fit and reflux and try again. Brute force won’t work, if you heat the back plate to the point that it’s glowing you’ll damage the sterling.
I’ll cover how I complete the construction and mount cabochons in my next post.
*Another approach (which I haven’t tried yet) is to use a soldering screen and tripod or ring stand. The advantage to this approach is that you heat the plate from below, and since it’s the largest mass of metal, the solder melts without danger of the torch flame melting the soft bezel ring.