I find most beginners and even many intermediate students use far too little heat when they are soldering. This often results in frustration that their solder won’t flow. The problem is, the longer it takes to get the metal to the flow temperature of the solder, the more oxygen comes in contact with the metal surface causing oxides to form. Once the solder oxidizes, as indicated by a darkening of the surface, it won’t flow or at best; won’t flow completely leaving a shadow of the pallion. At that point you might just as well turn off your torch, allow the metal to cool to dark heat, quench and pickle it. So, how do you avoid this? Use a hotter torch! Switch to a bigger tip, switch to a hotter gas, switch to an oxygen/gas torch or add an additional torch.
Clean your solder
Have you ever had the problem of getting your metal so hot that it starts to shimmer and yet your solder will not flow? By the time most students sign up for my intermediate/advanced metalsmithing class they are well aware that they need to clean their work before soldering. Oils on the surface of metal, from excessive handling, causes flux to bead up on the surface instead of sheeting across the entire surface. Without flux surface oxides develop quickly when the metal is heated. The same is true for solder and oxidized solder will not flow, no matter how hot you get it. So, before you light your torch, scrub your solder with a scouring pad and some pumice. It is good idea to get in the habit of doing this at the beginning of each work session. Even if you have not handled your solder, if it has been sitting around for more than a day or so, it will develop oxides.
The bigger the glob, the better the job?
No, most people use far too much solder. When solder flows it becomes so thin that its thickness is nearly inperceivable to the naked eye. Keep this in mind when cutting your pallions. With careful torch work and an appropriated size tip you should be able to use only enough so that this thin film just fills the seam. This not only minimizes clean up but also makes for a more professional looking join.
Jumping solder
Solder flows toward heat, so... if you don't heat, the metals being joined, evenly the solder will jump to the hottest part and completely ignore the other part of the join. Uneven heating can be caused by the following:
- A heat sink, ie. cross lock pliers not centrally located. If you are holding a ring shank, jump ring, bezel or the like, in tweezers, be sure there is an equal amount of mass on either side of the hold point. This is generally directly across from the join.
- Miss judging the mass of the two objects being joined. When joining items such as a thin bezel to a thick back plate, make sure you are applying proportionaly more heat to the larger mass.
- Differences in heat conductivity of dissimilar metals.
