Metalworks Minute: Annealing
Annealing is a critical process in the making of a hand built ring where the goldsmith is manipulating the metal with hammers, bending tools or rolling the surface. In this video, you can see the goldsmith heating the ring with a torch. This ring has been worked on till it is work hardened and now needs to be softened or annealed
Annealing means to heat the metal till it glows a dull to medium red. The high heat allows the crystals to re-form into a semi-ordered lattice formation. Gold and silver have cubic shaped crystals arranged in an ordered, re-ocurring pattern (called space lattice). The crystal structure is one important element determining a metal’s malleability: the inherent property that allows it to be formed by hammering, bending or rolling.
Metal is easily worked when the crystal patterns are semi-ordered: many of the clusters of crystals having the same order but not oriented in the same way —Think of a pile of “pick up sticks.” When a goldsmith works the metal the “pick up sticks” are broken down into smaller unoriented crystals. When metal becomes like this, it is then work hardened metal. If left in this hard state it will crack or be very hard to work.
The goldsmith returns the metal to a maleable state by annealing and then quenching the hot metal in water or a mild acid to arrest the re-organiztion of the crystals at the optimum moment.
Work can then continue.