Saturday, July 27, 2013

Answers to some Common Questions about Soldering

  • Sheet, wire and paste solder? When would I use one over the other?
More than anything, I think this is based on preference, especially with sheet or wire solder. I'm not a big fan of paste solders and how they work, nor of the fumes and toxins from the flux binders when they smoke and go airborne. Paste solders may still melt into a ball, once the flux burns off, but they can end up away from the join and make a mess. Otherwise, I prefer sheet solders for gold, since you can stamp the information on the sheet for karat, color and flow point. For sterling silver solder, I prefer wire, since I can cut it into ultra small chips or flatten it if I need sheet solder for tension or similar solder joins. Sheet and wire solder allow you to control the size and placement of solder in a way that can't be matched by paste, in my opinion, which is especially essential for cleanly soldering mixed metals. 
  • Why do I need a kiln brick? Can I just use a red brick I have in my backyard or a rock?
That's a good question and I can understand the confusion. A normal household variety brick is fire proof, but it's also a huge heat sink. Instead of helping, it will take heat away from the metal and it's pretty dirty, which can foul up the whole thing. Fire brick is used to make kilns, it's takes heat and amplifies it, making it easier to solder, and it's soft, which helps with positioning pieces for soldering. They may both have brick in their name, but they're completely different. Bonus: fire bricks are very light in comparison to building bricks. 
  • When do I use Easy, Medium and Hard solder? What is the difference?
Solders come in different melting points, called flow points, from high to low, or in jargon terms from hard to medium to easy. Using different temperature solders helps you fabricate more interesting jewelry, with lots of joins, without it falling apart or putting gaps in previous solder seams. Imagine trying to solder together a box with a stone setting. You can solder the walls together with hard solder, add a top and bottom with medium solder, and then attach jump rings and the stone setting with easy solder. The first, higher temperature hard solder joins won't open or fall apart as you add the rest of the pieces of the box with medium solder. When the setting is attached with easy solder, the medium and hard solder joins don't flow, preventing distortion or open seams. As you practice soldering and your skills improve, you'll spend more time using hard solder, until you're fabricating with only hard solder. One reason to prefer hard solder and use it as much as possible is the color. Hard solder has the least amount of additive to lower its flow point, so it matches sterling silver the best, making your joins almost invisible. 

  • When do I use Penny Brite and when do I use Pickle? What are the advantages of each?
Most jewelry studios use pickle to clean metal after soldering. It's easier and requires less scrubbing. Since natural, biodegradable pickles are now available for safe use at home, they're even safer and easier to use than more acidic pickles like Sparex. If after pickling there is still some residual firescale, you can use a brass brush or scotchbrite pad with soap and water, or Pennybrite to further clean the metal. But for my work flow, Pennybrite is just too labor intensive as a stand alone method for cleaning after soldering. Also, sometimes PennyBrite just won't get into the nooks and crannies of a more complicated design. Further, in cases of hard, baked on flux, the Pennybrite may not be able to remove the glass-like flux. You would have to soak the pieces in very hot water first, so you're basically pickling anyway.
  • Do the Jump Ring ends have to meet if I am soldering them together or will the solder fill the gap?
Solder doesn't like to fill gaps, and a "filled join" is weak and will break. For precious metal solders to work properly, the join must be completely closed. 

If the join is closed something very cool happens: the join will draw the fluid solder into the seam and into the metal, making a join so strong you could stretch a ring up to 2 sizes without it breaking! Why does it do this? When you heat the metal, it expands, creating a microscopic vacuum. That vacuum draws the solder into the seam when it flows, like a capillary action. No join - no vacuum. 

So, for example, if you're soldering a jump ring, and the join is not closed, the solder will just flow onto one end or the other, but not fill or close the ring. If you close the jump ring so that the ends of the join are touching and flush, then the solder will be drawn easily into the join. How can you tell if the jump ring is closed? Hold the join up to a low light source like a fluorescent light, and look through the join. If you see a line of light at the join, it's open. If you don't see any light, it's closed and ready to solder.
  • Can I use any kind of torch for soldering?
When you know how to solder, you can use just about any flame to solder, from plumbing blow torches to cooking torches, super hot oxygen/propane little torches to blow pipes and candles - no joke, in some countries, filigree is soldered with a candle flame and blow pipe to direct the heat. 

When I first learned how to solder in college, our only torch was a natural gas flame. It had a flame that was almost big enough for casting and we had to solder anything from tiny jump rings to bracelets with that flame. When you learn the art and craft of soldering, you learn how to adjust your torch for low and high heat, what distance you should be from the flame, where the hottest part of the flame is, etc. 

Now, of course, some torches are more ideal than others for soldering, but it depends on the material and the size of the job. If you have a big piece to solder and a small flame, you probably won't be able to heat the metal enough for the solder to flow. You need the right size flame for the job. For jump rings and simple wire pieces, a normal micro butane torch is fast and efficient. For bigger pieces like heavy gauge rings, larger settings, even bracelets, a large flame butane torch will cover more surface area and be able to heat the metal enough for the solder to flow. For gold, the same rules apply, so you can use butane torches with gold, but to really take advantage of the properties of gold, a oxy/propane little torch will let you solder faster and accurately. And let's face it, if you're soldering gold, you probably want the nicest toys to work with, right? 

For a free video on how to set up to solder safely at home, visit
  • How do I put the butane in the torch? 
Most butane torches will come with instructions for refueling and you should read those carefully - not just for refueling but also for how to light and safely use the torch. That said, a lot of butane torches refuel in the same way. First, your butane should be premium quality, the best you can afford. Cheap butane is greasy and can clog your torch. Make sure the nozzle on the butane canister fits the nozzle on your torch (on the bottom of the torch is a small recessed nipple that fits the nozzle for refueling). 

Interested in learning how to solder and getting some help? We have lots of classes in jewelry making, including casting, stone setting and working with gold at Silvera Jewelry School, in Berkeley, CA. Browse our calendar of classes today.