Annealing
4 of the 6 encyclopedias on this shelf carry an entry for Annealing. All 4 are reproduced below, so you can see where they agree and where they differ.
The Encyclopedia of Founding (1892)
The process of removing brittleness from castings, glass, and other substances by heating them to a specified temperature in suitable ovens or furnaces for a certain period, and then allowing them to slowly become cool again, prolonging the time in accordance with the nature of the article under treatment. Glass is heated to almost smelting heat to admit of a uniform arrangement of its molecules before it is in a suitable condition for grinding and polishing--from six hours to two weeks being required for this complete operation, according to thickness; heavy plate requires the longest time, the brittleness to which heavy steel-dies are subject is removed by placing them in water, heating to boiling, and then gradually cooled. Lead, tin, and zinc are annealed in the same manner. Heavy castings in bronze or cast iron may be partially annealed by slow cooling in hot cinders. Annealing is evidently the inverse process of tempering, the latter operation acting to fix the molecular condition of steel by a rapid (not a slow) change of temperature. See TEMPERING; MALLEABLE CAST-IRON; CAR-WHEEL. Animal Casts in Metal.--See INSECT CASTS IN METAL.
Aiton's Encyclopedia (1910)
the process of softening and toughening metals so that they are less brittle and more readily rolled into sheets or drawn into wires. Annealing is the opposite of tempering. Copper may be annealed by being plunged into cold water when at a white heat. Zinc heats and grows tough and flexible by the very process of being drawn into wire. Most metals are made flexible and tough by heating them until they are soft, and then allowing them to cool slowly, the more slowly the better. A blacksmith desiring to anneal a piece of iron heats it to a white heat, and then thrusts it into a heap of ashes, which conduct heat poorly, to cool off slowly. On the contrary a sudden plunge into a tub of water hardens or tempers a heated plowshare. Skill is required by the blacksmith to sharpen a plowshare and yet avoid the extremes of brittleness and softness. Wrought iron is, of course, annealed iron.
American Watchmaker and Jeweler (1892)
The process of heating metals and then manipulating them in order to increase their ductility. Gold, silver, copper and brass are annealed by heating them to redness and then plunging them in water, while steel is annealed by heating and then allowing it to cool slowly.
Collier's New Encyclopedia (1921)
a process to which many articles of metal and glass are subjected after making, in order to render them more tenacious, and which consists in heating them and allowing them to cool slowly.
What Has Changed in the Last Century
The practice these entries describe is still done daily, but the reason for it was unknown when they were written: only with the dislocation theory of 1934 (Taylor, Orowan and Polanyi) and later X-ray and microscope work did annealing become explicable as the recovery, recrystallisation and grain growth of a cold-worked metal, rather than a vague "uniform arrangement of its molecules." Modern annealing is done to measured temperature-time schedules in furnaces with controlled atmospheres, and the old confusion about opposites has been tidied up: tempering now means the gentle reheating of already-quenched steel, so annealing's true opposite is the quench, not the temper. The Encyclopedia of Founding's plate glass, annealed for up to two weeks and then ground and polished, was made obsolete by Pilkington's float-glass process of 1959, though glass is still passed through an annealing lehr to relieve stress.
Written for this edition, 2026.