Describe the process of annealing aluminium and explain the purpose of it.

Prepare the metal surface by rubbing it with a bar of soap. Place the metal against firebricks and use a gas torch to heat the metal surface evenly. When the soap turns black, stop heating the metal and allow to cool slowly.
Aluminium is annealed to reduce hardness and therefore reduce brittleness. It relieves internal stresses in the grain structure and increases the ductility of the material. This is useful as it allows the material to more easily be reshaped and be less likely to crack when subjected to impact.