A heat treatment where you heat a metal (or glass) above its recrystallization temperature, maintain the temperature, then allow it to cool. Annealing is conducted in order to increase its ductility and reduce its hardness. This process strengthens the metal (or glass) to make it more pliable and workable. During the annealing process, the number of dislocations in the crystalline lattice decreases, allowing its hardness to decrease and its pliability to increase. Hydrogen gas is frequently used to create an atmosphere for many metallurgical processes including annealing.