Infrared light is part of the electromagnetic spectrum with wavelengths ranging from 0.7 micrometers to 300 micrometers. Most of infrared light is emitted as thermal radiation from objects, most notably the sun. Many types of modern materials reflect infrared light due to their molecular composition. These reflective properties play important roles in infrared technology, ranging from automobile applications to clothing.
Gold, as the most malleable and ductile of all metals, can be beaten or coated on other materials in thin sheets. Because of its translucent quality, thin gold-leaf sheets are very good at reflecting yellow and red light. Because of this, gold is also efficient at reflecting infrared light. Gold coating is commonly used in a variety of applications as a method to reflect heat. Gold is incorporated as infrared shields in the visors of heat-resistant suits.
Aluminum is the most abundant metal found in the Earth's crust and is also the most commonly used metal in the industry today. Aluminum is useful because of its soft, durable and malleable physical properties; it can easily be machined, cast and drawn. In addition, aluminum possesses great capacity to reflect infrared radiation. Aluminum's infrared reflector qualities make it the ideal metal for infrared heaters. When coated with aluminum, the infrared heat is reflected and directed toward the product to be heated.
Plexiglas, a synthetic polymer used as a shatter-resistant alternative to conventional glass, also possesses a degree of infrared reflectance. Lightweight and flexible, Plexiglas is commonly used for paneling and daylight redirection. This material is valuable because it transmits most visible light, while reflecting and blocking infrared light of long wavelengths. By reflecting infrared radiation, the material dispels thermal heat for cooling purposes.
There are many different types of pigment coatings that will efficiently reflect infrared radiation. Hybrid pigmentation constructions made from a fibrous clay and dyes have been shown to have a high reflectance of the near infrared. Fibrous clays such as palygorskite and sepiolite are the best candidates for selection. Hybrid pigmentations are advantageous because they have superior physical and chemical properties than those of pure pigment or dye. Common applications for this technology include roof coatings and automobile coatings to increase thermal cooling.