Invisible rays just under the red end of the visible spectrum. Waves are longer than those of the spectrum colors but shorter than radio waves; they have a penetrating heating effect and, consequently, are used in cooking, photograph, etc.
Testing can be done either by inducing heat energy into an object, which is active, or by using the natural infrared energy of an object, which is passive. Testing is used to test insulation materials and installations, with variations of 0.01 degrees Fahrenheit able to be detected, as well as variations within the material being examined.
Chalk-like gray or white silicon, composed of fossilized remains of marine life, which is used for thermal insulation for steam piping, paint extenders, scouring powders, filters, etc. Also called Tripoli or Diatomaceous Earth or Diatomaceous Silica.