US Patent 7207193 Method of fabricating low-warp flat glass

A method of fabricating a glass sheet comprises modifying the thermal stress in the glass such that it is a tensile stress or substantially zero stress in a particular temperature zone of the glass, with that zone selected such that the glass sheet is formed substantially free of warping. In an example embodiment, the modifying of the thermal stress is effected by non-uniform cooling of the glass across the glass transition temperature range. This non-uniform cooling may be applied in cooling segments that are linear and at least two of the segments have differing slope.