Abstract: The invention relates to a process for reinforcing a glass object by precompressing the surface of the object, acid etching said surface to a depth equal to or less than the compressed depth of the glass, and finally protecting the etched surface.

Abstract: This invention has as its subject a panel, preferably produced by the float process, reinforced by surface ion exchange for a long period at a temperature such that the exchanged depth is greater than 250 microns for surface compressive stresses exceeding 400 MPa, and greater than 75 microns for surface compresive stresses exceeding 700 Mpa, and the matrix of which complies with one of the following compositions, expressed in percentages by weight:SiO.sub.2 :65 to 76%Al.sub.2 0.sub.3 :1.5 to 5%MgO:4 to 8%CaO:0 to 4.5%Na.sub.2 :10 to 18%K.sub.2 O:1 to 7.5%B.sub.2 O.sub.3 :0 to 4%these elements representing at least 96% of the weight of the glass and complying, in addition, with the percentages by weight 0<CaO/CaO+MgO<0.45 and 0.05<K.sub.2 O/Na.sub.2 O+K.sub.2 O<0.35.

Abstract: A method for the preparation of glass sheets with a view to laminating them consists of curving the glass sheets by causing them to pass one after another along a curved trajectory, then cooling them by passage between blowing chests, and of dispatching them by batches to the assembling station, and a laminated pane, the sheets of which have, in the central zone, a core compressive stress of from 1 to 50 MPa.

Abstract: A method for the preparation of glass sheets with a view to laminating them consists of curving the glass sheets by causing them to pass one after another along a curved trajectory, then cooling them by passage between blowing chests, and of dispatching them by batches to the assembling station, and a laminated pane, the sheets of which have, in the central zone, a core compressive stress of from 1 to 50 MPa.