The Colours Produced in Glasses by Exposure to Radiations
JSGT 1956 V40 T187-T251
The coloration produced in various series of glasses by exposure to ultra-violet radiation and to X-radiation of high energy has been studied. The 'radiation colours' which develop in glasses containing iron or manganese are consistent with the generally accepted modem view that the coloration is of two types, caused by absorption resulting from: (i) increase of valency of some constituent ion or ions which can exist in two or more valency states, and (ii) the displacement of electrons from ions in the glass to sites where an anion is missing from the glass structure. The effects of arsenic, titanium, and cerium, alone or present together, on the development of ferric iron colour in glasses which contained small amounts of iron were studied, and also the effects of arsenic on the development of the purple manganese colour in glasses containing manganese in small proportions. Most of the work was done on soda–lime–silica glasses, but observations were also made on a series of alkali–lead–silica glasses and on a few borosilicate and boro-aluminate glasses. A study was made, later, of the marked fading of the 'radiation colour', which was found to occur when the irradiated glasses were kept in the dark at room temperature. The observations on the fading suggested further work on a series of binary soda-silica glasses, and out of this work certain conclusions were tentatively drawn concerning the types of vacant sites in which electrons may be trapped in the structure of silicate glasses. Observations on a binary lime-silica glass, of a composition 'equivalent' to that of a binary soda–silica glass of high soda content, suggest strongly that the Ca2+ ion has an appreciable bonding action in the glass structure.
P. L. Baynton & H. Moore
