Solder
Solder is the metal alloy that is melted to join the lead came or copper foil in a stained glass panel. The traditional mixture is tin and lead, most commonly 60 percent tin and 40 percent lead, which melts at a convenient temperature and flows well. Lead-free solders, based mostly on tin with a small amount of silver or copper, are also available.
Each type behaves differently. A tin-lead solder spreads and gives a smooth bead, while lead-free alloy is stiffer and needs a hotter iron and good flux. A flux is always used to clean the metal and help the solder to flow.
Soldering produces fumes, so good ventilation and clean hands are essential, and the finished panel is often cleaned and treated with a patina.