60/40 Solder is 60% tin and the balance lead. A consistent and smooth flowing solder, 60/40 is the best selling ally in the stained glass fied. It melts are 372 F, and solidifies at 361 F. The "pasty range" (most solder melt at a higher temperature than they freeze at, the difference between these figures is the pasty range) of 60/40 is smaller than that of 50/50, giving the user a smoother bead.