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Glossary

B

Beveling
The process of edge finishing flat glass to a bevel angle.

Bullet-resistant glass
A multiple lamination of glass or glass and plastic that is designed to resist penetration from medium-to-super-power small arms and high-power rifles.

Bulletproof Glass
Armour plate glass which is more than 60 mm thick and which resists penetration by bullets.

C

Coated glass (reflective glass)
Float glass clear or coloured, one side of which has been coated with a very fine layer of metal oxides. It allows active regulation of daylight and solar heat and glare. It absorbs a certain amount of solar heat and simultaneously reflects another and it transmits a certain amount of solar light ant at the same time it reflects another. Besides the thermal and light performance it adds a high aesthetic touch wherever applied. There are two kinds of coatings:

a. the hard coating (also called pyrolytic) reinforces the low-e and/or the solar performance of glass. It is applied using a high-temperature and penetrates the surface of the glass, becoming remarkably durable. This last property means that processors can process those products very easily.

b. the soft coating (also called magnetron) is applied by projecting metal particles onto the glass using a vacuum electromagnetic process. The composition of this coating depends on the desired colour and features.

D

Double glazing
When any two glass panes, separated by an air or gas space, within an opening, to improve insulation against heat transfer and/or sound transmission. In insulating glass units the air between the glass sheets is thoroughly dried and the space is sealed, eliminating possible condensation and providing superior insulating properties.


E

Edging
The shaping or finishing of the edges of a glass surface, usually by grinding with an abrasive wheel.

Emissivity
The measure of a surface's ability to emit long-wave infrared radiation.

Energy Absortion (EA)
Percentage of solar energy flux absorbed by the pane or panes making up the glazed wall. The absorbed energy is then reradiated to the outside or inside at different rates depending on the characteristics of the pane or panes of glass, wind speed, internal air speed, internal and external temperatures.

Energy Reflection (ER)
Percentage of solar energy flux reflected by the glass.

Energy Transmission (ET)
Percentage of solar energy flux transmitted directly through the glass with a spectral density (between 300 and 2150 nm).

Engraving
The production of a design in glass by cutting into the glass surface. Engraving methods include copper wheel engraving, diamond or tungsten point engraving, acid etching and sand blasting.

F

Facade (face)
The whole exterior side of a building that can be seen at one view; strictly speaking, the principal front.

Figured Glass
Patterned glass is a translucid glass made from clear or coloured cast glass that passes between two rollers located at the end of the glass furnace. The pattern is printed at high temperatures on one side of the glass by the engraved (embossing) roller. temperature.

Fibre Glass
Very fine strands of glass (normally with a high boric oxide and content) used in the form of glass wool for insulation, glass fibre for matting, etc., and also for the reinforcement of plastics. The principal production process involves blowing jets of steam or air onto molten glass as it emerges from a tank furnace through very small diameter nozzles.

Fire-resisting Glass
Flat glass with a wire inlay which helps retard shattering in the event of fire and thus delays the spread of smoke and flames.

Float glass
Float glass is the product of sand and sodium carbonate heated to more than 1.500°C and running off over a bath of molten tin.

Float Process
A method for the production of high-quality float glass whereby a ribbon of molten glass is fed across a bath of heated liquid, usually molten tin, in a carefully controlled atmosphere. The process was developed by the UK firm Pilkington Brothers.

G

Glass
A homogeneous material with a random, liquidlike (non-crystalline) molecular structure. The manufacturing process requires that the raw materials be heated to a temperature sufficient to produce a completely used melt, which, when cooled rapidly, becomes rigid without crystallizing.

Grinding
The removal of glass with abrasives or abrasive (grinding) wheels in order to shape, polish or otherwise finish both flat and hollow glass. Grinding processes include milling, sawing, edging and drilling.

H

Heat-absorbing glass
Glass that absorbs an appreciable amount of solar energy.

Heat-resisting glass
Glass able to withstand high thermal shock, generally because of a low coefficient of expansion.

Heat-treated
Term used for both fully tempered glass and heat-strengthened glass.

Heat Resistant Glass
Glass which has a low coefficient of expansion and which is therefore less liable to thermal shock.
High Performance Thermal Insulating Glass
Thermal insulating glass to which an extremely fine, invisible coating of precious metal is applied, giving the glass considerably greater power of insulation against heat loss and cold.

High-transmission glass
Glass which transmits an exceptionally high percentage of visible light.

I

Insulating glass unit (IG units)
Two or more lites of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between each lite.

Interlayer
Any material used to bond two glass panes and/or plastic together to form a laminate.

K

K- or U- VALUE
The heat transfer coefficient (k- or U- value) is the amount of heat in watts per unit of time, which is transferred through 1 sq.m of glass surface per degree Kelvin difference between internal and external temperature. The k- or U- value is calculated for the wall's surface heat exchange coefficients:
- internal : 8 W/m2K
- external: 23 W/m2K.


L


Laminated Glass
Laminated glass consists of two or more glass panes with one or more viscous plastic layers "sandwiched" between the glass panes. The solid joining of the glasses takes place in a pressurised vessel called an autoclave. In the autoclave, under simultaneous heating of the already processed layers of glass and special plastic, lamination occurs. When laminated safety glass breaks, the pieces remain attached to the internal plastic layer and the glass remains transparent.

Light Reflection (LR)
Ratio of the light flux reflected by the glass to the incident light flux

Light Transmission (LT)
Ratio of the light flux transmitted through the glass to the incident light flux expressed.

Low Emissivity Glass (Low-e)
Also called "low-E" glass and often used in double and triple glazing units, this window glass has a special thin-film metallic or oxide coating which allows the passage of short-wave solar energy into a building but prevents long-wave energy produced by heating systems and lighting from escaping outside. Low-E glass thus allows light to enter while also providing thermal insulation.

M


Mirror
Clear or coloured high quality float glass with a silver layer deposited on one side of the glass to obtain a light reflection of more than 92 %. The silver layer receives a special treatment, and is then protected by two different layers of special protective paint.


P

Patterned Glass (see also Figured Glass)
Glass to which a pattern is applied by passing it while still soft between two rollers, one of which has a decorative pattern engraved on its surface.

PVB
An abbreviation for polyvinyl butyral. PVB is used in sheet form as a strong plastic interlayer in the production of laminated glass.

R

Reflective Glass (see also Coated Glass)
Glass with a metallic coating to reduce solar heat gain.

S

Safety Glass
Glass which does not disintegrate into sharp and potentially dangerous splinters when it is broken. Safety glass may be produced in two ways: a. by laminating (see "laminated glass") or b. by tempering (see "tempering").

Sand Blasting
A method for giving glass surfaces a matt finish either for decoration or to reduce transparency.

Shading Coefficient (SC)
The shading coefficient is obtained by dividing the solar factor by 0.87, which is the solar factor of 3 mm clear float glass.

Single glazing
A single pane of glass.

Solar glass (Solar Control Glass or Energy Glass)
Tinted and/or coated glass that reduces the amount of solar heat gain transmitted through a glazed product. They have been reinforced with one or more extremely thin layers of metal oxides. Their key function is to reduce the Total Energy Transmition (Solar Factor or Solar Heat Gain). This type if glass ensures optimum quality of natural light without need to use artificial light during daytime.

Solar energy reflectance
In the solar spectrum, the percentage of solar energy that is reflected from the glass surface(s).

Solar energy transmittance
The percentage of ultraviolet, visible and near infrared energy within the solar that is transmitted through the glass.

Solar Factor (SF)

  • sun at 30° above the horizon at right angles to the facade
  • ambient temperature equal to outside ambient temperature
  • surface heat exchange coefficients

- internal : 8 W/m2K
- external: 23 W/m2K.

Solar heat gain coefficient
The ratio of the solar heat gain entering the space area through the fenestration product to the incident solar radiation. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation which is then reradiated, conducted, or convected into the space.

T

Tinted glass (Colored Glass)

Glass with colorants added to the glass mass that gives color, as well as, light and heat-reducing capabilities. The color extends throughout the thickness of the glass. Typical colors include bronze, gray, dark gray, aquamarine, green, deep green, blue and black.

Tempered glass
A strong, break-resistant glass made by speeding the cooling process by immersing the molten glass in water. The resultant glass has a surface compression five to ten times more resistant to mechanical and thermal shocks than well-annealed glass.

Thermal Shock Testing
Assessing the effects on a material of rapid temperature change. In glass, the shock may derive from the external surface of glass expanding or contracting more rapidly than the interior surface as a result of heating or cooling. Any such difference may lead to cracking or shattering.

Translucent Glass
Permitting light to come through but diffusing it so objects on the other side appear vague, distorted, or imperfect.

Tempered glass
Float glass that has been thermally treated to give it a higher degree of mechanical and thermal resistance. The glass is first heated to more than 600° C, then cooled down quickly (full toughening or tempering) or cooled down more slowly (heat strengthening), in both cases at a carefully controlled speed. These processes put the surface of the glass under permanent compression stress, giving the glass its special characteristics.
Resistance to mechanical and thermal shocks up to 2 times (heat strengthened) or at least 5 times (toughened) higher than normal float glass.
Prevents glass from breakage caused by high temperature differences on the surface of the glass pane (caused by shadows for example). This is particularly important for glass types with a high energy absorption that are exposed to heat radiation.
Only for toughened glass: safety glass that breaks into small fragments without cutting edges, ensuring protection against risks of injury.

Transmittance
The ability of the glass to pass light and/or heat, usually expressed in percentages (visible transmittance, thermal transmittance, etc.).

Transparent or Clear Glass
Permitting light to come through without distortion so objects on the other side can be seen clearly.

U

Ultraviolet (UV Rays)
The name of the invisible portion of the light spectrum with wavelengths shorter than 390 nanometers.

U-value
A measure of air-to-air heat transmission (loss or gain) due to the thermal conductance and the difference in indoor and outdoor temperatures. As the U-value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-value, the more restrictive the fenestration product is to heat transfer.

W

Wired glass
Rolled glass having a layer of meshed or stranded wire completely imbedded as nearly as possible to the center of thickness of the lite. This glass is available as polished glass (one or both surfaces) and patterned glass. Approved polished wired glass is used as transparent or translucent fire protection rated glazing. Patterned wired glass is sometimes used as decorative glass. It breaks more easily than unwired glass of the same thickness, but the wire restrains the fragments from falling out of the frame when broken.

 
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