This resource provides enrichment and extension for pupils studying metal reactivity. Copper is low on the reactivity scale. This low reactivity, combined with its malleability makes it ideal for use in architecture. It can be cut and hammered into ornate shapes and it will protect itself with a pale green coating of copper salts called a patina. Etching is a basic tool to reveal the grain structure of copper. The etchant attacks the polished copper surface selectively revealing the size and shape of the grains.