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
Fourcault process By changing the chemistry it is possible to affect the surface characteristics of the glass, improving its quality and durability. Glass rollers hold the ribbon throughout various parts of the process, supporting its weight and continuing the drawing process. The process continues as the ribbon is drawn upwards into a chimney like structure, where it is quenched or rapidly cooled. When the ribbon reaches the end of the process it is scored, or cut, and then removed for further processing in discrete sheets of flat glass. The "bulb edges" are recycled as cullet (flawed glass which is remelted) or were