117 alloy used for blocking is a Eutectic Fusible Alloy and its primary component is Bismuth. (The price has gone up, up, up over the past 18 months)
Fusible Alloys include a group of binary, ternary, quaternary, and quinary alloys containing Bismuth, lead, tin, cadmium and indium. The term fusible alloy refers to any of the more than 100 white-metal alloys that melt at relatively low temperatures.
Bismuth 44.7%
Lead 22.6%
Tin 8.3%
Cadmium 5.3%
Indium 19.1%
Tin Anodes