Reducing the warp of sheet glass

— Many leading technologies, such as flat‐panel displays and precision optics, require sheet glass with exceptional surface qualities. Commercially available sheet glass of <1 ‐mm thickness typically has a surface warp on the order of hundreds of microns, rendering it a challenge to utilize progressively thinner sheets. A novel method of shaping individual sheets and ribbons of glass is presented which utilizes porous mandrels. This method reduces the surface warp of the ribbon while in its hot state without contacting its surface. Sheet glass is inserted between two parallel porous mandrels spaced apart by a predefined distance. A thin layer of pressurized gas flows through each mandrel and out against the glass surfaces. The local gap between the warped glass sheet and the flat mandrel determines the local pressure on the glass. When in its heated and soft state, the glass sheet's surface is changed by this pressure with a strong restorative force proportional to the inverse of the gap cubed, which tends to flatten the sheet. By using flat mandrels and controlled pressurized gas at elevated temperatures, the outcome is a sheet of glass with a surface warp of a few microns while retaining its original pristine optical surface qualities.