Magic metal

Fusible alloys

When teaching metals there are a number of ways to show how mixing metals together can alter their properties. Fusible alloys (ones which melt at a low temperature) are an attractive and underused opportunity to show how far we can manipulate a material's properties.

Fusible alloys are used for solders, as temperature triggers in sprinkler systems (where the plug is held in place with a fusible alloy which melts in a fire), as mercury replacements (eg galinstan thermometers) and even as experimental coolants in fast neutron reactors.

Field's metal is one such alloy which melts at a low temperature (61°C) and, unusually for a fusible alloy, contains neither lead nor cadmium.

Kit

• Sample of Field's metal (~30 g is a good size)
• Ceramic crucible
• 250 cm³ conical flask
• Optional moulding paraphernalia (eg ice cube trays, plasticine, jewellery moulding compound)