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EFFECT OF TEMPERATURE ON HOMOGENIZING RATE OF SODA‐LIME‐SILICA GLASS *
Author(s) -
Tiede R. L.,
Tooley F. V.
Publication year - 1945
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1945.tb14510.x
Subject(s) - soda lime , soda lime glass , materials science , flat glass , atmospheric temperature range , mineralogy , composite material , silica glass , glass furnace , maximum density , analytical chemistry (journal) , chemistry , thermodynamics , chromatography , physics
A bstract Density‐spread determinations were made on a series of melts of a soda‐lime‐silica glass prepared at temperatures ranging from 1232° to 1454°C. for a four‐hour period in the absence of furnace refractory and under conditions of minimum convection mixing. A sharp drop in density spread in the range 1232° to 1288°C., a minimum at about 1325°C., and a slowly increasing density spread at temperatures above 1325°C. were observed. The portion of glass responsible for the major part of the density spread was found to be concentrated in the top half of the glass at both 1232° and 1454°C. At the higher temperature, the improvement in the homogeneity of the bottom layer was more marked than that observed in the top layer as compared with the results obtained on the lower‐temperature melt. The density spread of the glass in the bottom layer in the case of the high‐temperature melt was in the range of that observed for commercial soda‐lime‐silica glass of good quality. A possible explanation for the observed increase in density spread at higher temperatures (above 1325°) is offered on the basis of more rapid initial segregation during melting at higher temperature as inferred from the density‐spread data and from chemical analyses of the glass from the top and bottom portions of melts made at 1232° and 1454°C. Loss in weight of the glass due to volatilization was determined at 1232° and at 1454°C. and was found to amount to less than 0.01% for a four‐hour melting period at both temperatures. Moderate mixing, achieved by repeated cracking and remelting of the glass and by melting in a rotating tilted crucible, had a marked effect in lowering the density spread. The data afforded by these experiments lend further emphasis to the view that convection currents in commercial tank operation are highly significant in improving the homogeneity of a soda‐lime‐silica glass.