ANNEALING, a process to which metals and glass are subjected in order to increase their ductility, or lessen their liability to frac ture under sudden stress. It is usually effected by heating the substance to be annealed until it approaches softness, and then allowing it to cool very slowly. Copper, however, is best an nealed by heating it to a high temperature and then plunging it immediately into water. Met als that are to be annealed should be heated in close vessels, so that they may not be affected by direct contact with the fuel It is not un common to anneal large masses of metal or glass by allowing the fires in the heating fur nace to go out, and permittin the furnace and g_ its contents to cool together. The articles to be annealed are also often buried, while still hot, in lime, ashes or some other poor conductor of heat and left until cold. Metals that are to be drawn into wire or rolled into sheets, or pressed into complicated shapes, usually require an nealing during the process, as otherwise they are likely to become brittle and crack or break. Zinc, however, grows strong and flexible as it is drawn into wire, though it loses its flexibility and regains its crystalline structure if kept in boiling water for a time. It is usually taught
that the object of annealing is to soften the material sufficiently to allow molecules to move slightly among themselves, and thus relieve the strains previously introduced by sudden cooling, or by the violent stresses to which the material has been subjected in thy process of working. This theory is very possibly true to a certain extent, but the anomalous cases of copper and zinc, cited above, show that it can be regarded only as a first approximation to the ideal theory of annealing, which has yet to be discovered.
See TEMPERING.
an'se, town of eastern France, situated in the central part of the department of Haute Savoie at the northwest end of Lake Annecy. It has manufactures of silk, cotton, wool and steel, and contains many buildings of historical interest, including a cathedral and the old castle of the counts of Genevois. Pop. about 15,000.