Water and water vapor can degrade the mechanical strength of glass, promote crack growth, and cause fatigue.^1,2

Water has been found to enter through the fracture surface of glasses,^3,4,5 indicating that water ahead of the crack tip promotes the growth of cracks. Both structural⁶ and stress relaxation⁷ were found to occur faster at the glass surface than in the bulk when exposed to water. Liquid water or water vapor in the air can enter the glass through diffusion. At low temperatures, molecular water can remain in the glass. At high temperatures, most of the diffused molecular water readily reacts with the glass network to form immobile hydroxyls, ≡Si-OH.^8,9