Annealing (metallurgy) brass can be cooled slowly in air, or quickly by quenching in water, unlike ferrous metals, such as steel, which must be cooled slowly to anneal. In this fashion, the metal is softened and prepared for further work—such as shaping, stamping, or forming. Annealing occurs by the diffusion of atoms within a solid material, so that the material progresses towards its equilibrium state. Heat increases the rate of diffusion by providing the energy needed to break bonds. The movement of atoms has the effect of redistributing and eradicating the dislocations in metals and (to a lesser extent) in ceramics. This
History of glass in sub-Saharan Africa be shaped, heated and cooled. The archaeological evidence of beadworking in Sub-Saharan Africa provides examples of both types.5 9 With melted glass working, beads found were generally formed by either a wound, drawn or moulded process. Wound glass beads, also known as Tubular, Cylindrical, Spherical or Melon-Shaped, were formed by folding molten glass around a metal rod called a mandrel. Once the glass had cooled slightly, the material was slipped off the mandrel and pinched and prodded until it reached a desired shape.9 Also known as Cane beads, Drawn beads were formed by dipping an iron blowpipe into molten glass