SE354266

Process to strengthen the glass and increase its resistance to surface abrasion, characterized by comprising: A) the treatment of the surface of the glass with a compound containing a metal from the group consisting of tin, titanium and zirconium, the compound of which is pyrolyzable to form a metal oxide on the surface of the glass while said surface is at a temperature at least as high as the pyrolyzing temperature of the compound, B) a subsequent spraying of said surface with an aqueous solution of a potassium salt to form a continuous coating layer thereon while said glass is still at an elevated temperature in the field near the point of tension of the glass, C) the maintenance of glass at an elevated temperature below the glass tension point for a sufficient period of time to achieve a significant exchange of sodium ions and potassium ions from the glass to a sufficient depth to produce a significant compression stress, although not for a sufficient time to produce a relaxation of tension, D) the cooling of the glass and its subsequent washing to remove any excess potassium salt from the surface of the glass, and. E) a further spraying on the glass surface of an olefin polymer in an amount sufficient to form an adherent and transparent coating on said surface. (Machine-translation by Google Translate, not legally binding)