Emissivity
The ratio of radiant energy emitted by a surface to the radiant energy emitted by a black body of the same temperature.

Explosion
A sudden release of energy resulting in a blast wave.

Figured / Patterned Glass
Figured / patterned glass is produced domestically by the continuous pour process in thicknesses of 1/8" to 7/32". A pattern etched on one or both of the rollers is reproduced on the glass. Colors are available but are extremely limited. This type of glass is frequently called "obscure" or "decorative" glass. The pattern diffuses detail of objects viewed through the glass, it does not obscure them. The degree of diffusion achieved is a function of the pattern and whether the pattern is on one or both sides. Some patterns cannot be tempered for safety glazing use because of their depth.

Float Glass
The float glass process accounts for over 90% of the flat glass presently produced in the United States. In this process, molten glass is poured continuously from a furnace onto a large bed of molten tin. The molten glass literally floats on the tin, spreading and seeking a controlled level in the same manner as water poured onto a smooth, flat surface. In the controlled level seeking process, the molten glass is allowed to spread to width of 90" to 140", depending upon the furnace size and glass thickness being produced. The glass slowly solidifies as it travels over the molten tin. It is then cooled under controlled conditions. Afterward, it emerges as a continuous ribbon of glass at essentially room temperature. The product is now flat, fire-finished, and with virtually parallel surfaces.

Glass Edge Strength
(1) Glass is made to withstand from between 3000 to 5000 psi (210 to 350 kg/cm) of edge stress. (2) When edge stress exceeds edge strength, breakage occurs. (3) Edge strength depends on glass size, thickness, how it is cut, and treatment of edge by glazier. (4) A straight clean edge is the strongest. (5) Damaged edges can reduce edge strength by up to 50%.

Ground Zero
The location at which an explosion occurs.

Heat Strengthened Glass
Heat strengthened glass is fabricated by a process similar to that of tempered glass. Some equipment can produce both. The glass is heated to approximately 1100° F and the cooling process is slower than for tempered glass. The strength developed is about twice that of annealed glass.

Hot Spots
Areas particularly affected by solar radiation and the imbalance of solar energy.