different tensile strength. Ballistic glass and laminated glass are both rated to different standards and have a different shatter pattern. Heat-strengthened glass Heat-strengthened glass, or tempered glass, is glass that has been heat treated to induce surface compression, but not to the extent of causing it to "dice" on breaking in the manner of tempered glass. On breaking, heat-strengthened glass breaks into sharp pieces that are typically somewhat smaller than those found on breaking annealed glass, and is intermediate in strength between annealed and toughened glasses. Heat-strengthened glass can take a strong direct hit without shattering, but has a weak edge. By simply tapping the edge of heat-strengthened glass with a solid object, it is possible to shatter the entire sheet. Chemically strengthened glass Chemically strengthened glass is a type of glass that has increased strength. When broken it still shatters in long pointed splinters similar to float (annealed) glass. For this reason, it is not considered a safety glass and must be laminated if a safety glass is required. Chemically strengthened glass is typically six to eight times the strength of annealed glass. The glass is chemically strengthened by submerging the glass in a bath containing a potassium salt (typically potassium nitrate) at . This causes sodium ions in the glass surface to be replaced by potassium ions from the bath solution. Unlike toughened glass, chemically strengthened glass may be cut after strengthening, but loses its added strength within the region of approximately 20 mm of the cut. Similarly, when the surface of chemically strengthened glass is deeply scratched, this area loses its additional strength. Chemically strengthened glass was used on some fighter aircraft canopies. Low-emissivity glass Glass coated with a low-emissivity substance can reflect radiant infrared energy, encouraging radiant heat to remain on the same side of the glass from which it originated, while letting visible light pass. This often results in more efficient windows because radiant heat originating from indoors in winter is reflected back inside, while infrared heat radiation from the sun during summer is reflected away, keeping it cooler inside. Heatable glass Electrically heatable glass is a relatively new product, which helps to find solutions while designing buildings and vehicles. The idea of heating glass is based on usage of energy-efficient low-emissive glass that is generally simple silicate glass with special metallic oxides coating. Heatable glass can be used in all kinds of standard glazing