Last Updated: Jul 19, 2016     Views: 17

I consulted with our Research Scientist, Dr. Robert Brill, about your query regarding the pH range expected for a powdered glass in water. Dr. Brill replied:

"I can't give a definitive answer. To whatever extent water will extract alkali from a very finely powdered glass (the powder having a large surface area), I would expect that the water will become slightly alkaline. The pH change would depend on the composition of the glass, temperarture, and time of exposure to the water. Glasses with lower chemical durabilities (alkali silicates, for example) will produce a greater effect than more durable glasses (borosilicates or alumino-silicates.) One method of measuring the relative durabilities of glasses is the so-called powder test in which glasses are exposed to water under carefully controlled conditions. The method depends upon the analysis of the alkali extracted, but would probably also ordinarily cause a corresponding elevation of pH."

He suggests that details of the test could be obtained from Corning Inc., Research Center at Sullivan Park (try their Technical Informtion Center, 607-974-3258) or the ASTM.