The Tinted Glass (heat absorbing glass) is made by adding color pigments to the raw materials in the float process. Standard colors include bronze, gray, dark gray, green, blue and blue/green. Imported glass may be in non-standard colors. The color density is a function of thickness, as the glass gets thicker the density of the color increases and the amount light transmittance decreases. Because tinted glass reduces the amount of light transmitted, it also absorbs some of that solar energy, called heat absorption. This added heat causes thermal stress which may affect the glass and can cause it to break if it is not tempered.