The alloy name tin lead antimony is used to describe a mixture of tin, lead and antimony in different proportions depending on the casting process. The most common use of tin lead antimony is for printing type for mechanical line and individual character hand setting. It is also used for stereo plate casting. The addition of tin to lead reduces the shrinkage during solidification making the letters produced sharper and stronger to resist wear and pressure. Pure lead is soft and easy to work but it has little tensile strength; it is also a very poor cast metal. Lead alloys can be made with a wide range of alloying elements to improve the performance, usually adding tin and/or antimony for hardness. Other metals such as silver are added to make the alloy harder, more resistant to corrosion and less brittle. Lead-antimony alloys are also commonly found in storage battery grids and general manufacturing.
The tin lead antimony alloy is made by introducing powdered stibnite and scrap iron into a crucible with the aim of producing metallic antimony. When the crucible is melted with the addition of the two materials and the temperature lowered, this produces a 4/12 eutectic mixture that has a clear melting point at 252 degC. When this melt is allowed to cool it will crystallize forming grey powder (dross) which must be skimmed off. During the production of type metal this is repeated many times as the dross contains recoverable tin and antimony which would otherwise be lost through oxidation. This dross is processed at specialist companies to extract the pure metals for further manufacture.