Solder 101: Forms and Melting Temperatures for Soldering Jewelry
Soldering is one of the most basic techniques in metalworking, but also one of the hardest to master. For a very good reason, we are taught in early childhood to fear fire, and the possibility of melting a piece that has a lot of work (and expensive materials) in it is always present. However, as with any process that has a certain mystique about it, understanding how and why soldering works will make us much more comfortable with it. Especially knowing why the process works will let us do some intelligent troubleshooting, rather than simply guessing when a problem arises.
There are five basic areas that make up the soldering process: solder, flux (an oxygen-reducing compound that coats and protects the piece during the soldering process to help prevent oxidation), heat (jewelry-making or hand torch), fit (the edges being joined should fit tightly) and cleanliness (make sure your hands, metals and tools are clean of dirt and oils, as pieces won’t join together if any component is dirty). If the optimum conditions are maintained in each of these five areas, the soldering process will go smoothly. It is when we begin to “fudge,” or get sloppy, that things go wrong. Knowing why something happens will let us solve the problem quickly. Even the pros sometimes have to go back to basics!Soldering is the process in which two or more pieces of metal are joined together using a metal alloy (solder). The metal alloy has a lower melting temperature than the metals being joined. The area where pieces of metal are joined is called a joint. Hard soldering is also called low-temperature brazing. Soft soldering uses very low melting temperature solder alloys, usually of tin and lead, and is not commonly used in fine jewelry.
Solder is a nonferrous (without iron) metal alloy, the major percentage of which is usually the same as the metal being joined: gold, silver, copper or brass. Gold solder is available in different colors to match various alloys. Because brass and copper solder, also known as brazing rod, has a high melting temperature and is brittle, silver solder is usually used on these metals as well as on silver. All of the nonferrous metals (gold, silver, copper, brass or bronze) that have a relatively high melting temperature can be soldered with either gold or silver solder. Both gold and silver solders are available in different melting temperatures and are manufactured in several forms.
Forms of solder include sheet, wire, pallions (clippings or chips) and paste. Which form of solder to use is a matter of training and personal choice. I prefer to use sheet cut into small pallions, because wire solder, being round, will sometimes roll away from the force of the flame; sheet stays where you put it (usually). Paste solder, a mix of tiny bits of solder mixed with a paste flux, is used primarily by mass producers in machine soldering and is the most expensive form of solder. It typically comes prepared in a syringe and is often used for delicate and intricate work such as filigree. Knowing how much paste solder to use requires a bit of experimenting.
Melting temperatures of solder are determined by the zinc content: the higher the zinc content, the lower the melting temperature. Zinc is what turns the lower melting temperature silver solders a yellowish-gray; to avoid conspicuous solder lines, use the highest temperature solder feasible. Pits in the solder seam are caused when the solder is overheated and the zinc burns out. Again, using a higher temperature solder (and controlling the heat) will help to prevent pitting.
The most common silver solder melting point divisions are:
- IT: The highest melting temperature, used on fine silver when enameling (melting point: 1490 degrees Fahrenheit)
- Hard: Used for bezels and as a first step when doing multiple soldering (melting point: 1425 degrees Fahrenheit)
- Medium: Used mostly when only one or two steps will be done (melting point: 1390 degrees Fahrenheit)
- Easy: Used as a final solder or when soldering on findings (melting point: 1325 degrees F)
- Extra Easy: Used primarily for repairs and is distinctly yellow in color- (melting point: 1270 degrees Fahrenheit)
Gold solders come in hard, medium, easy and extra easy as well as different karats and colors. One manufacturer has recently come out with a medium hard silver solder, with a melting temperature between that of hard and medium solder.Because sheet and wire solder are indistinguishable from regular sheet and wire metal, these solders should be marked as soon as they are purchased. Sheet solder can be scribed with 1, 2, 3 or H, M, E (for hard, medium, easy); wire solder can be hammered or even have knots tied in one end. In order to distinguish between the different melting temperatures, some schools like to use a different form for each; wire for hard, sheet for medium and flattened wire for easy.
Why use different melting temperature solders? When fabricating a complicated piece, using different melting temperature solders will help prevent the previously soldered joints from remelting and either shifting or coming unsoldered. The first components assembled are joined using the hardest solders, which melt at very high temperatures; as each additional metal component is added, lower temperature solders are used. The goal is simple: Bonding pieces together without accidentally melting the previous soldered joint.
There is no industry standard for exact melting temperatures, and each solder manufacturer has its own specifications. Therefore, buying all your solder from one source will help keep the different melting temperature solders straight, although a combination of solders from different manufacturers may give you more versatility.
You will often see two temperatures listed: a melting point and a flowing temperature, which is higher. The melting temperature is when the solder starts to melt, and the flow point occurs when the solder is completely molten. The difference between these two temperatures, or spread, can be from 25 degrees Fahrenheit to more than 100 degrees Fahrenheit. It’s important to know the spread, because it will affect where and for how long you apply the heat. Experimenting with solder from different sources will give you the opportunity to find just the right combination that suits you.
Final Tips on Soldering Jewelry:
- Ventilate soldering area: Be sure to use proper ventilation to safely remove fumes from your working area.
- Proper heating: Apply heat only to metals being joined, and heat the metals uniformly, avoiding heating one area too much.
- Use sufficient flux: In addition to helping prevent oxidation and protecting the metals being joined, flux allows the solder to flow more easily between the joints being joined.
–Sara M. Sanford
If you’re interested in learning more about soldering and how to solder jewelry, learn from the master jeweler who taught me. Get Lexi Erickson’s five-star-rated soldering DVD, Metalsmith Essentials: How to Solder Jewelry, available in DVD and HD download.
(Sara M. Sanford is a professional jeweler and founding member and past president of the Creative Metal Arts Guild in Portland, Oregon.)