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.

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.

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.

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.

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.

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.

Thermally treating a glass sheet by holding the glass sheet between first and second gas bearings, the glass sheet having first and second major surfaces on opposite sides thereof and an edge surface surrounding the sheet and connecting the first and second major surfaces, the glass sheet being held with the first major surface adjacent to the first gas bearing and the second major surface adjacent to the second gas bearing, a glass of the glass sheet having a glass softening temperature, and, while holding the glass sheet between the first and second gas bearings, maintaining the glass sheet at a viscosity (t) for a time t such that the value of the expression (30 MPa times the integral from 0 to t of t/(t) with respect to t) is within the range of from 10 to 10.sup.6.

Thermally treating a glass sheet by holding the glass sheet between first and second gas bearings, the glass sheet having first and second major surfaces on opposite sides thereof and an edge surface surrounding the sheet and connecting the first and second major surfaces, the glass sheet being held with the first major surface adjacent to the first gas bearing and the second major surface adjacent to the second gas bearing, a glass of the glass sheet having a glass softening temperature, and, while holding the glass sheet between the first and second gas bearings, maintaining the glass sheet at a viscosity (t) for a time t such that the value of the expression (30 MPa times the integral from 0 to t of t/(t) with respect to t) is within the range of from 10 to 10.sup.6.

A strengthened architectural glass or glass-ceramic sheet or article as well as processes and systems for making the strengthened architectural glass or glass-ceramic sheet or article is provided. The process comprises cooling the architectural 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 architectural glass sheets that may be incorporated into one or more panes in single or multi-pane windows.