Stained glass artists are concerned with the mechanical and the artistic factors.
The Solder Alloy
In any soldering procedure a mechanically reliable joint is essential, but for Stained Glass work the appearance of the completed joint is also vitally important.
1). The solder joint must blend into the shape of the material being soldered.
2). The surface of the completed joint must be smooth and free of any bumps or grittiness.
3). As the solder oxidizes from exposure to the air, or the application of any metal coloring agents, the fillet should develop the same patina as the remainder of the metals.
The standard 63/37 tin/lead alloy remains the easiest solder to use. It melts at 183C and has no pasty phase, changing directly from solid to liquid and back to a solid. This means that the solder solidifies instantly producing a very smooth fillet, with no ridging or other marking which may be caused if the joint moves during solidification. The 60/40 alloy produces almost similar results at a slightly lower cost, but with a slightly higher melting point and a small pasty phase.
When cost is a major concern, solders with a lower tin content can offer some savings. However as the tin content is reduced, the solders have a higher melting point and as they cool, they pass through a pasty phase. This can produce a frosty appearance to the solder fillet and of course will leave striations or cracks if the joint moves during cooling. The higher meting point also means that soldering has to be carried out at a higher temperature. In general therefore, the 63/37 eutectic tin/lead solder is easier to use and produces a better looking joint. Solders with a higher proportion of lead are cheaper but less forgiving. .
Lead-Free Solders
Several lead-free alloys are available, and are similar in performance to the lower tin content solders mentioned above. With normal care there is little or no jeopardy to the operator in the use of lead bearing solders. (Click for article “Lead-Free”) Their chief environmental threat lies in the disposition of scrap metals which should always be returned for recycling.
Selecting the Soldering Iron
Ideally the iron should always operate at the same temperature. This is almost impossible to achieve, as the moment the tip touches the joint the temperature begins to fall rapidly. With an uncontrolled iron this means you will be soldering at varying tip temperatures. Minimize the variation by using a reliable temperature controlled soldering iron.
Buy an iron with a chisel bit, as large in diameter, and as short as is convenient to use. If you will be soldering many joints at a time make sure the iron wattage is sufficient to maintain a constant temperature. The tip should stay at least 100C above the solder melting temperature during the entire soldering process.
Patina
Make the joint quickly and try to avoid an “second soldering”. The objective must be to use the right iron and the right technique so that the joint is made correctly the first time with the solder flowing smoothly into the overall shape of the design. When this can be achieved and the solder is made from clean, pure base metals, there is seldom any problem in developing an excellent appearance.
Hirsch metals sells a variety of solders for the stained glass artist.