US Patent 9751802 Heat treatment for strengthening glasses

A method of making a strengthened glass article. The method includes altering the glass structure and subsequently creating a compressive layer extending from the surface of the glass to a depth of layer. In some embodiments, the structure is altered by heat treating the glass at a temperature that is less than the annealing point of the glass, and the compressive layer is formed by ion exchange. A strengthened glass article made by the method is also provided.