Architectural glass light in industrial factories. Annealed glass is glass without internal stresses caused by heat treatment, i.e., rapid cooling, or by toughening or heat strengthening. Glass becomes annealed if it is heated above a transition point then allowed to cool slowly, without being quenched. Float glass is annealed during the process of manufacture. However, most toughened glass is made from float glass that has been specially heat-treated. Annealed glass breaks into large, jagged shards that can cause serious injury and is considered a hazard in architectural applications. Building codes in many parts of the world restrict the use of annealed glass
Heated glass surface of the glass between the busbars must be flat. An electric current flows across the tin(II) oxide coating from one busbar to the other. The electrical resistance of the coating produces heat energy, which radiates from the glass. The busbars are connected to a power control unit that regulates the flow of electricity and thus the temperature of the glass. In modern architectural projects the heated glass is completely translucent. This technology uses a special metallic coating on the surface of the glass invisible to the naked human eye. A pane of heated glass can achieve temperatures up to