Reflected Pressure
The amount of pressure felt by an object standing directly in the path of an expanding blast wave.

Reflective Glass
Reflective glass is a clear or tinted glass coated with an extremely thin layer of metal or metallic oxide.

Rolled Glass
The rolled glass process consists of pouring molten glass from a furnace, then feeding it through rollers to produce the desired thickness. The glass ribbon is then cooled under controlled conditions. There are three general types of rolled glass: figured / patterned, wired and art / opalescent / cathedral glass.

Shading Coefficient (SC)
The ratio of solar heat gain passing through a glazing system to the solar heat gain that occurs under the same conditions if the window were made of clear, unshaded, double strength window glass. The lower the number, the better the shading qualities of the glazing system.

Sheet Glass
The Sheet glass process accounts for a very small portion of U.S. glass production. Some imported sheet glass will continue to be used, mainly in thickness of 1/8" and less.

Side-on Pressure
The pressure felt on the sides and top of an object as the blast pressure wave envelops and passes over and around it.

Sill
The horizontal structure that supports the upright portion of a window frame.

Spandrel Glass
Spandrel glass panels are heat strengthened or tempered glasses with a ceramic frit color permanently fused to one of the surfaces. Glass in spandrel areas is not subject to corrosion as are some other spandrel materials. Pleasing aesthetics and economies can be obtained using a single framing system for an entire wall. Glass spandrel panels can also save energy when insulation is placed behind them.

Standoff Distance
Generally speaking, the further you are from a blast, the better your opportunity to survive. Each site should be evaluated to assess its structural strength, window frame type and attachment, and glass type to determine which style of film application would be most appropriate to withstand the blast at a given distance.

Tempered Glass
Tempered glass is fabricated by subjecting annealed glass to a special heat-treating process. The most commonly used process is to heat the glass uniformly to approximately 1150° F, and then rapidly cool it by blowing air uniformly onto both surfaces simultaneously. The cooling process locks the outer surfaces of the glass in a state of high compression and the central portion, or core, in compensating tension. The color, clarity, chemical composition and light transmission characteristics remain unchanged. Likewise, compression strength, hardness, specific gravity, expansion coefficient, softening point, thermal conductivity, thermal transmittance and stiffness are unchanged. The only physical property that changes is tensile or bending strength. Under uniform loading, tempered glass is about four times stronger than annealed glass of the same size and thickness, and is thus more resistant to thermally induced stresses, cyclic wind loading and hail stone impacts. When broken, tempered glass breaks into a multitude of small fragments of more-or-less cubical shape. Therefore, it qualifies as a safety glazing material under the criteria of Federal Standard 16 CFR 1201 and the American National Standards Institute (ANSI) Z97.1-1984, when so labeled and certified. Spots or blotches may, at times, be visible on tempered glass, especially when viewed through polarizing lenses or in certain types of reflected light. The intensity will vary with lighting conditions and viewing angle. This is caused by the strain pattern induced during the cooling stage, and is not inherently a cause for rejection.

Thermal Stress
(1) All glass absorbs energy when exposed to solar radiation. (2) Tinted glass absorbs more energy than clear glass. (3) Occurs when there is a temperature differential between center of glass and shaded edges. (4) The ability of the glass not to break is determined by its edge strength.

Tinted / Heat Absorbing Glass
Tinted or heat absorbing glass is made by adding various colorants to the normal, clear glass batch to create a desired color. The four colors available by the float process are bronze, gray, green and blue. Visible light transmittance will vary from 14% to 83%, depending upon color and thickness. The color density is a function of thickness, and increases as the thickness increases; visible light transmittance will decrease as thickness increases. Tinting reduces the solar transmittance of glass, has little effect upon solar reflectance, and hence increases solar absorption (heat). This explains why heat strengthening or tempering is sometimes required for the thicker tinted glasses. Adding a metallic coating also has the same effect on thinner glasses.

TNT Equivalence
The quantity (Ib / kg) of an explosive material expressed in terms of the equivalent mass of TNT required to generate similar blast values.

Total Solar Absorption
The ratio (percentage) of the total amount of solar energy that is absorbed by glass compared to the amount of total solar energy that hits the glass. This solar energy is neither transmitted through the glass nor reflected back out into the atmosphere.

Total Solar Reflectance
The ratio (percentage) of total solar energy which is reflected outward by glass compared to the total amount of solar energy falling on the glass. (Use of window film can affect this.)

Total Solar Transmittance
The ratio (percentage) of the amount of total solar energy in the entire solar wavelength range that passes through glass compared to the amount of total solar energy falling on the glass. (Use of window film can affect this.)

Transmissivity
The amount of radiant energy transmitted from a radiating object through the atmosphere to a target after reduction by atmospheric absorption and scattering.