Note on the Viscosity of Some Glasses of Abnormal Working Properties

JSGT 1929 V13 T070-T076

 In a series of papers contained in this volume it has been shown that glasses· of the same chemical composition appear to possess different working characteristics according to the conditions under which they have been prepared. Thus, the presence of considerable amounts of moisture in the batch led to the production of glasses which, when worked into rod and tubing, had an increasingly greater working viscosity and rate of setting as the amount of moisture was increased. Glasses prepared from mixtures of batch and cullet containing progressively increasing proportions of cullet showed similar behaviour; and so also, under the conditions of our experiments, did a series of glasses prepared from a batch in which the limestone was of a coarse grading. The possibility of inhomogeneity by the glass as a cause for such increase in the working viscosity and shortening range of the glass was considered, and in the case of the glasses prepared from varying proportions of cullet the content of sodium oxide was also carefully scrutinised without any indication of a cause for the phenomenon observed. When the glasses of abnormal working viscosity were broken up small and re-melted so as to ensure homogeneity, good working glass was obtained, but the working viscosity and rate of setting in all cases were still further increased.

S. English & W. E. S. Turner