Effect of Stress on Durability of Ion‐Exchanged Surfaces

The leachability of ion‐exchanged alkali alumino‐silicate glasses in water and in acid was shown to be a function of the stress at the surface. Alkali aluminosilicate glasses formed by ion exchange under conditions resulting in surface compression were more durable than similar unstressed alkali aluminosilicate glasses melted from batch. Conditions which produced incomplete exchange at the surface, resulting in lower compressive surface stresses, led to a less durable glass surface. Where potassium from a salt bath was being exchanged for sodium in the glass, leachability was inversely proportional to the percent surface exchange.