An article of fire rated glass and method of producing the same prepared by selecting a sheet of clear float annealed glass of at least 19 millimeters in thickness and providing the edge of the sheet substantially free of imperfections. The glass sheet is then specially tempered at a temperature of at least 575 degrees Celsius for a period of at least 750 seconds, followed by a cooling step.

An article of fire rated glass and method of producing the same prepared by selecting a sheet of clear float annealed glass of at least 19 millimeters in thickness and providing the edge of the sheet substantially free of imperfections. The glass sheet is then specially tempered at a temperature of at least 575 degrees Celsius for a period of at least 750 seconds, followed by a cooling step.

An article of fire rated glass and method of producing the same prepared by selecting a sheet of clear float annealed glass of at least 19 millimeters in thickness and providing the edge of the sheet substantially free of imperfections. The glass sheet is then specially tempered at a temperature of at least 575 degrees Celsius for a period of at least 750 seconds, followed by fluid quenching.

An article of fire rated glass and method of producing the same prepared by selecting a sheet of clear float annealed glass of at least 19 millimeters in thickness and providing the edge of the sheet substantially free of imperfections. The glass sheet is then specially tempered at a temperature of at least 575 degrees Celsius for a period of at least 750 seconds, followed by a cooling step.

A laminated glass article comprises a core layer comprising a core glass composition having an average core coefficient of thermal expansion (CTE.sub.core) and a clad layer directly adjacent to the core layer and comprising a clad glass composition having an average clad coefficient of thermal expansion (CTE.sub.clad) that is less than the CTE.sub.core such that the clad layer is in compression and the core layer is in tension. A compressive stress of the clad layer increases with increasing distance from the outer surface of the clad layer, transitions to a minimum tensile stress as a step-change at an interface region between the core layer and the clad layer, and a magnitude of the tensile stress increases continuously to a maximum tensile stress in the core layer. Other stress profiles, and methods of preparing laminated glass articles are also disclosed.

A glass sheet forming and annealing system disclosed provides control of edge stresses by maintaining a press formed glass sheet on an annealing ring (72) below a heated upper forming mold (58) within a forming station (12) for slow cooling toward the glass strain point temperature.

In a method for tempering a glass sheet, based on identified glass sheet properties, a tempering furnace temperature and/or glass sheet heating time are adjusted, the blowing pressure and/or distance of cooling unit air jets are adjusted, the glass sheet is heated in a tempering furnace, the achieved temperature is thereafter measured from the glass sheet surface, and the glass sheet is cooled. The development of the thickness direction temperature profile of the sheet during the tempering cooling is calculated, the residual stress profile achieved in the glass sheet during tempering is calculated, a reference variable for the glass sheet tempering level is selected and the selected reference variable is compared to a predetermined threshold value. If the comparison between the reference variable and the threshold value fulfils a predetermined criterion, an alarm is created and/or the glass sheet is found not to qualify as safety glass.

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 pre-stressed structure and a method for forming a pre-stressed structure are provided. The pre-stressed structure comprises a panel including a first region pre-stressed into a condition of membrane tension, resulting in the panel having increased transverse stiffness. The pre-stressed structure may further comprise a second region pre-stressed into a condition of membrane compression. The panel may be a plate or a shell and may form part of an insulating glass unit, which in turn may form part of a curtainwall unit.

The disclosure relates to glass compositions having improved thermal tempering capabilities. The disclosed glass compositions have high coefficients of thermal expansion and Young's moduli, and are capable of achieving high surface compressions. A method of making such glasses is also provided.