Brass in course of time undergoes a molecular change which renders the alloy very brittle, and this action sometimes causes cracks to open in the metal, particularly if it is subject to variations of temperature when moisture is present. Brass wire when subject to tension rapidly loses its working properties. In either of the above cases the alloy is known as " rotted " brass, and may be distinguished from new-made brass by bending it sharply to an acute angle; if signs of partial fracture are quite absent, the metal may be used.