Spontaneous glass breakage is a phenomenon by which toughened glass (or tempered) may spontaneously break without any apparent reason. The most common causes are: * Minor damage during installation such as nicked or chipped edges later developing into larger breaks normally radiating from point of defect. * Binding of the glass in the frame, causing stresses to develop as the glass expands and contracts due to thermal changes or deflects due to wind * Internal defects within the glass such as nickel sulfide inclusions * Thermal stresses in the glass * Inadequate glass thickness to resist wind load