July 2020

Q:  How do I keep solder from re-flowing when I have to perform a second or third soldering? I’m using sterling silver and my bezels something open when I try to solder them to a back plate.

A: I will limit my answer to sterling silver—there are some techniques that work with other metals but don’t work as well on sterling due to its high conductivity.

The melting temperature of solder rises every time you heat it, so on a second soldering process with the same grade of solder (extra-easy, easy, medium, hard, IT), the solder should flow before the previous join melts. Good heat control comes with practice and experience, and many experienced jewelers only use one grade for everything, but that doesn’t work for everyone.

One way to make it easier on yourself is to use a lower grade solder on a second join. If you used hard solder for the first join, like on a bezel, use medium solder to attach the bezel to the back plate. Then if you want to add embellishments, you can use easy or extra easy for the next procedure. Be sure to watch for the solder to flow—if you keep heating your piece after the lower temper solder has flowed, you can still cause the higher temper solder to flow because silver conducts heat so well (and you can get annoying pitting, too). So pay attention to your heat control and remember that more is not always better when it comes to heat.

Another way to do this is to use a solder flow retardant. Here are a few choices:

-Yellow ochre. This generally comes as a powder to be mixed with water to form a thick paste which can then be brushed onto the area where you don’t want the solder to flow to as well as to the previous join. Don’t mix it too thin or it will take a long time to dry. Drying is essential before applying your flux so you don’t have them flowing together. Available from most supply houses.

-Wite-Out Correction Fluid. This can be painted on like the yellow ochre. There is some discussion as to whether to use oil- or water-based and I have not gotten a good answer on whether the oil-based is toxic when heated, so I don’t use it anymore.

-Graphite. You can rub a graphite stick or soft pencil lead over the part you want protected, or you could use liquid graphite. Hard pencil lead can contain polymers which are flammable, so it’s best to avoid them. Most art supply stores have graphite sticks.

-Powdered rouge. You can scrape off some of your polishing rouge or collect some dust from around your polishing equipment, dampen it a bit, and then paint it on where you want it.

-Commercial products. The only commercial product I have used is Rhonda Coryell’s Masking Mud which works very well. While originally made for Argentium, it works well on other metals too.

Keep making great things! Stay safe and well, and send your questions to askmassc@gmail.com