Abstract: A glass sheet to be heated, for example to a bending or a quenching temperature, is supported on its lower edge in an upright disposition and is advanced along a horizontally disposed path through a furnace. Transient support is provided for the upper edge of the sheet which support is positioned to cause the sheet to lean at a near-vertical angle as it is advanced, and thermal conditions in the furnace as well as the time the sheet is within the furnace are set in dependence on the glass thickness so as to heat the glass to the required temperature while permitting the glass to relax as it is heated only by an amount less than a maximum acceptable deformation of the sheet which depends on the use to which the sheet is to be put.