After 25 years as a jeweler, first as a student, an apprentice, an instructor, and now a master instructor and director of the Jewelry Arts Institute in New York City, I’ve come to realize that much of the basic information about soldering being taught to students is misleading and confusing.
There are many myths about heating pieces during soldering that can cause innumerable problems during relatively simple soldering operations. In this new occasional column, I will address the top soldering myths and the essential criteria to be used in evaluating soldering techniques.
Since the cone is the hottest part of the flame, you should use it for soldering
Almost any beginning jewelry student can tell you they have read or been told by instructors that the hottest part of the flame is the cone (Figure 1). This is factually accurate. However, there is a difference between the part of a torch flame where the temperature is highest and the part that can transfer the most heat to the work.
The trouble comes when students interpret the cone being the hottest part of the flame to mean they should try to place the cone of the flame as close as possible to what they are trying to heat (Figure 2). This is ineffective, causing the majority of the flame’s heat to be released beyond the piece and leaving the students to wonder why their solder oxidizes and refuses to flow.
After doing repeated testing in the studio over many years, I’ve found that pieces heated with the end of the flame (Figure 3) reach soldering temperatures more quickly because they are receiving all of the flame’s heat, rather than just the heat from the cone. There’s also less oxidation than when the cone of the flame is used because the piece heats faster.
In addition, using the end of the flame gives you more control over the heat. When soldering, you want to withdraw the heat as soon as the solder has flowed where you want it. If you don’t cease heating, the solder will continue to flow, possibly to where you don’t want it.
I’ve found that the natural reaction to remove the flame is to pull it back up, not off to the side. If you’re heating with the flame’s cone (Figure 4), pulling it up will leave the rest of the flame heating the joint for an extra second or two. This additional heating time could mean the difference between a perfectly soldered seam and a sloppy, overheated seam with pits.
To help avoid this, position the torch as illustrated in Figure 5, using the far end of the flame to heat the seam. This positioning will provide the ideal situation: fast and controlled heating.
This article is excerpted from “Soldering Demystified,” a paper presented at the 2015 Santa Fe Symposium on Jewelry Manufacturing Technology. To order a copy of the paper, visit santafesymposium.org.