A method and an apparatus for tempering glass sheets. A glass sheet is heated to a tempering temperature and quenching is conducted by blasting cooling air to both surfaces of the glass sheet. The quenching of a top surface and a bottom surface of the glass sheet's both side portions is commenced earlier or is performed at the early stage of quenching more effectively than the quenching of a top surface and a bottom surface of the glass sheet's intermediate portion. As a result, the compression stress required for a desired tempering degree is established on both surfaces of the side portions earlier than on both surfaces of the intermediate portion. In order to achieve this, the cooling air enclosures above and below a glass sheet are provided with a subarea of weakened cooling effect.

A strengthened glass sheet product as well as process and an apparatus for producing the product. The process comprises cooling the glass sheet by non-contact thermal conduction for sufficiently long to fix a surface compression and central tension of the sheet. The process results in thermally strengthened glass sheets having improved breakage properties.

Methods of shaping a glass sheet are described comprising heating the glass sheet to a temperature for shaping; positioning the glass sheet on a shaping support; shaping the glass sheet on the shaping support, wherein during the shaping of the glass sheet at least one portion of the glass sheet is deliberately cooled. In preferred embodiments, the shaping of the glass sheet involves press bending a heat softened glass sheet between a lower shaping support and an upper shaping member, and wherein during the shaping of the glass sheet on the shaping support only a portion of the major surface of the glass sheet facing the lower shaping support is cooled by directing one or more jet of air onto said portion.

The present disclosure relates to a method for tempering a glass sheet to a surface compressive stress of at least 150 MPa, without hair cracks, to optically good quality and energy-efficiently. Quenching is carried out when the glass sheet travels through a quenching section by blowing air jets on upper and lower surfaces of the glass sheet by a blower, through blowing apertures in the cover of a blowing box and by air compressor pressure through pipe nozzles. In the quenching section, both above and below the glass sheet, are at least three successive compressed air convection blowing zones with separately adjustable blowing pressures. Zone-specific differences in the heat transfer coefficient are implemented by changing the blowing pressures of the pipe nozzles.

A method for evaluating the sensitivity of a glazing to forming quench marks depending on its anisotropy, the sensitivity being evaluated by computing parameter σ.sub.v, the quench marks resulting from different optical phase shifts in different regions of the glazing for a vision in transmission or reflection and from either side of the glazing, the method including computing a transmission parameter T1, T2 through face 1 or 2 or a reflection parameter R1, R2 from face 1 or 2, this computation being done for a region of the glazing without optical phase shift and for a region of the glazing inducing an optical phase shift δ; computing a parameter ΔE(δ) corresponding to the color difference between said regions, based on at least one of T1, T2, R1, R2, and computing σ.sub.v by applying a function G dependent on computed ΔE(δ) and where appropriate on the one or more corresponding δ.

An invention is provided for creating smoothed, heat-treated glass fragments. The invention includes placing a plurality of heat-treated glass fragments into a tumbling or vibrating apparatus. Each heat-treated glass fragment is formed from glass that has been heated to a temperature of at least 1000° Fahrenheit and rapidly cooled to a temperature below 800° Fahrenheit. The plurality of glass fragments is then tumbled or vibrated for a predetermined period of time such that surfaces of the heat-treated glass fragments are smoother than prior to tumbling. The glass fragments are thereafter removed from the tumbling apparatus, resulting in smoothed, heat-treated glass fragments that have a slightly rounded, bead like-shape and are suitable for direct handling without hand protection. The glass fragments as are able to be provide radiant heat in the temperature range of 400° to 800° Fahrenheit. This temperature range and the use of the heat-treated glass fragments provides for a clean burning fire that virtually eliminates any soot and carbon monoxide while burning.

A process for the manufacture of a heat strengthened glass substrate, includes the application of a temporary layer including a polymer on a glass substrate including a glass sheet, then the application to the glass substrate coated with the temporary layer of a treatment for the heat strengthening of the glass including heating, leading to the removal of the temporary layer, and then cooling by blowing of air through nozzles. The glass substrate thus obtained exhibits a reduced level of iridescences.

A glass substrate comprises: a first position, wherein a tensile stress of the glass substrate is insufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate; and a second position, wherein the glass substrate is bent relative to the first position, and wherein the tensile stress of the glass substrate is sufficient to cause fragmentation of the glass substrate into small pieces upon fracture of the glass substrate. The glass substrate can include a first surface and a second surface. In the first position, the first surface and the second surface of the glass substrate can be planar. In the second position, the first surface and the second surface of the glass substrate can be planar. The small pieces can be generally cubic. In the second position, the glass substrate can be bent uniaxially along a bend axis of the glass substrate.

A method for the production of glass ribbon portions is provided that includes: transporting a glass ribbon at a velocity v.sub.1, wherein the velocity v.sub.1 is dependent on the predetermined glass thickness (d.sub.1), with the application of a tensile stress parallel to the edges of the glass ribbon, in a plane E.sub.1, and cooling the glass ribbon at a cooling rate that is dependent on the predetermined glass thickness (d.sub.1), inserting a score on the surface of the glass ribbon in at least one edge area by scoring the glass surface with a scoring tool, wherein the score has an angle a to the transport direction of the glass ribbon, deflecting the glass ribbon in a plane E.sub.2 to generate a bending stress and separating a glass ribbon portion with the formation of edges by breaking the glass ribbon on the extension of the score running transversely to the glass ribbon.

A strengthened cover glass or glass-ceramic sheet or article as well as processes and systems for making the strengthened glass or glass-ceramic sheet or article is provided for use in consumer electronic devices. The process comprises cooling the cover glass sheet by non-contact thermal conduction for sufficiently long to fix a surface compression and central tension of the sheet. The process results in thermally strengthened cover glass sheets for use in or on consumer electronic products.