Interaction of water with glass at very high temperature under dynamic condition and the properties of the obtained glass surface

A conventional soda–lime–silicate glass-melt was treated with water vapor during the course of cooling from 1300 to 600 °C in less than a minute. The water vapor was generated spontaneously from a wet porous carbon substrate beneath the glass-melt. Within the treated glass surface, sodium was found to be depleted more and deeper than calcium. The morphology of the treated surface was found to be very smooth and homogeneous without defects (mean roughness Ra=0.26 nm), unlike the water treatment at lower temperatures where the glass surface suffers from corrosion. As a consequence of the lower alkali concentration and homogeneous morphology, water vapor-treated surface showed improved chemical stability. The results are considered to be brought about by the combined effects of the alkali ion depletion through ion-exchange with hydronium ion, hydration, followed by the repeated hydrolysis and reformation of SiOSi bond. These processes are believed to be accelerated significantly at high temperatures.