Lost Foam Casting
The most basic way to cast metal is 'lost foam' casting. This process is based on the evaporation of polystyrene foam when it comes in contact with the liquid metal. As polystyrene burns it leaves only gaseous substances so they will not contaminate the casting.
The process starts with creating the desired pattern out of foam. To aid PVA-adhesive and masking tape can be used. A sprue to feed the molten metal must be added to the pattern by glueing on a rectangular piece of foam.
Once the pattern is created it can be buried in very dry sand, with the sprue projecting above the sand. When molten metal is poured in the sprue, the foam will evaporate and the metal will fill the cavity created by the evaporation. To help direct the metal into the sprue it's very handy to thin can or piece of tubing to locate around the sprue.
To make castings with a higher surface finish, the pattern can be coated with plaster. This way the metal will not come in contact with the sand, since the plaster should withstand the temperature of the liquid metal.
The process starts with creating the desired pattern out of foam. To aid PVA-adhesive and masking tape can be used. A sprue to feed the molten metal must be added to the pattern by glueing on a rectangular piece of foam.
Once the pattern is created it can be buried in very dry sand, with the sprue projecting above the sand. When molten metal is poured in the sprue, the foam will evaporate and the metal will fill the cavity created by the evaporation. To help direct the metal into the sprue it's very handy to thin can or piece of tubing to locate around the sprue.
To make castings with a higher surface finish, the pattern can be coated with plaster. This way the metal will not come in contact with the sand, since the plaster should withstand the temperature of the liquid metal.