SELENIUM RUBY GLASS*

Abstract

ABSTRACTThis paper presents the results of an experimental study on the production of selenium ruby glass, particularly on the retention of the colorants during the melting and fining operations. Selenium, cadmium, and sulfur are necessary in the final glass to get a ruby color. Reducing conditions are conducive to the retention of a large percentage of the selenium in the glass, but when conditions are highly reducing, cadmium is eliminated almost completely. The writers believe that too little attention has been given in the past to the chemistry of the entire glass batch, and as a result operators and research workers have often failed to get a ruby glass not because the loss of selenium was too high but because they eliminated the cadmium by maintaining too strongly reducing conditions.A balance must be maintained so that the batch and the atmosphere above it are sufficiently reducing to hold enough selenium in the melt but not so strongly reducing as to eliminate the cadmium.Most of the work reported in this paper was done on soda‐lime‐silica glasses similar to those melted in continuous tanks for the production of machine‐made ware. A glass of this composition, containing 0.03% of selenium, 0.06% of cadmium, and 0.03% of sulfur, will produce a ruby color. The writers have found that if the cadmium is added as cadmium sulfide the final glass will have sufficient sulfur for color development. The use of silicon as a reducing agent is suggested.An arrested‐cooling procedure for developing color is described briefly.