The Annealing Temperatures of the Lime-Soda Glasses
T125-T128 (4 pages)
Concerning the variation of the annealing temperature with the composition of the glass, only the main outlines are as yet known. Practical experience has laid down the rules that lead glasses are readily annealed, whilst chemical glassware, on the other hand, requires a high annealing temperature followed by slow rate of cooling if strain is to be first removed and then prevented from recurring. The actual data for certain general classes of glassware, including lead glasses, lime glasses, boric oxide-containing, and chemical glassware, have been determined previously by us and discussed in a previous number. In so far as we can ascertain, however, no scientific worker has yet made an attempt to study the effect of the variation of composition in any one of these types and thus ascertain clearly what is the effect of the presence of a definite constituent. The results now described, therefore, open out a new field, whilst the information is of importance in view of the fact that the lime–soda series of glasses is of the greatest commercial importance, and since the proportion of lime used for different types of glassware may vary considerably, it is very desirable to set down the proper conditions for their treatment in the lehr.
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