Abstract
SHEFFIELD. Society of Glass Technology, October 20.—J. W. French: Glass annealing. In any discussion of annealing the first question is the rate at which heat is dissipated by glass at the various temperatures of the annealing process. The other conditions determining the magnitude of the stresses that may be established in glass during the cooling process are: (2) The thermal expansion in contraction of the material; (3) thermal conductivity; (4) cohesion of the material; (5) the viscosity of glass; (6) the existence of a surface layer having properties different from those of the underlying material; (7) homogeneity of the glass; and (8) the form and dimensions of the glass. From the optical glass point of view, annealing means—(1) the raising of the temperature to a point just above that of the softening point of the hardest glass in the charge, and (2) the cooling of the plant at a rate which will not at any one point be sufficient to reintroduce stresses in any of the glasses.—E. A. Coad-Pryor: The economics of the annealing process. An account was given of experiments on which the Engineering Department and the Research Laboratories of the United Glass Bottle Manufacturers, Ltd., had been recently engaged at Charlton. In order to get the information on which to design a lehr on a sound theoretical basis, it was necessary to know the amount of heat taken into the lehr by the bottles and the heat lost through the lehr walls. Eventually heat was supplied to the lehr by means of the slats of the conveyer. During most of the period of testing, the lehr was running at about one-third of its maximum speed. The annealing was good throughout. When it was speeded up to its maximum rate, about 10 inches a minute, the annealing remained excellent, even on quart bottles. This speed represented an output of 450 gross of quarts per day, or about 40 tons of glass. The lehr was fitted with a number of curtains to restrict draught up the tunnel. Once the: curtains were adjusted to the correct setting, no further adjustments were required.—F. A. Hurlbut: A suggested improvement in the design of lehr conveyer.—E. Meigh: A new type of “fireless” lehr.
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Societies and Academies. Nature 118, 681–682 (1926). https://doi.org/10.1038/118681a0
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DOI: https://doi.org/10.1038/118681a0