There are four types of glass in general use: annealed, wired, toughened, and laminated. Laminated glass is produced by taking two or more sheets of annealed glass and sandwiching PVB between them; the heat-based process causes the plastic to clarify and adhere permanently to the glass on either side, making it very hard and enabling it to absorb shock. The British Standards Authority has published guidelines dictating the use of laminated and other types of glass. Alternatives to laminated glass include polycarbonate and glass reinforced plastic, which is a translucent material. Before installing laminated glass, any security director must consider the level of protection required, the weight of the complete installation, and cost. Laminated glass can incorporate alarm sensors as well as environmental features including light sensitivity, antiglare properties, and special coatings to reduce emissions from computer terminals.