Glassary - D

Data protection:
the electromagnetic shielding of computers either to prevent scanning of the radio waves emitted by computers or to prevent corruption of data by interference from outside radio or radar sources.

Datastop™:
Pilkington Datastop™ is the brand name for a range of laminated glass and insulating glass units that have been specifically designed to give increased electromagnetic shielding for computers and offices.

dB:
see decibel.

dBA:
a weighted measure of sound that is designed to stimulate that of our ears. The international standard for this measure is called the 'A' Weighting Curve. Measurements made with this facility are, therefore, termed 'A' weighted decibels or, more concisely, dBA, to discriminate from those made in plain dB, which do not depend directly on human reaction.

Decibel (dB):
the scale used to measure or describe

Loudness of sound or

Sound insulation and sound reduction indexes (see acoustic performance), or

Attenuation of radar and radio waves (see electromagnetic shielding).

Deep Flemish™:
is the brand name for an old Pilkington patterned glass, which is no longer manufactured. It had an obscuration level of 2.

Deflection:
how much something moves out of true plane when a load is applied. Glass can bend when a load like snow or wind is applied. Deflections can be calculated in advance and the correct glass for the application specified.

Desiccant:
a chemical drying agent that dries and helps remove any organic vapours from the air or gas trapped inside the cavity of an insulating glass unit. It is sometimes called a molecular sieve.

D.G.U.:
double glazing unit.

Diamond Leading:
a style of leading copying a traditional leaded light.

Diffusing:
randomly scattering the incident light while still allowing transmission. Usually applied to the effects on light of acid etching, sand blasting and 3065 white tinted interlayers. (See also translucent.)

Diffusion:
see diffusing.

Dimensions:
the length and width or other appropriate descriptions of the size of a pane of glass. The glass thickness is not usually referred to as a dimension of the glass.

Direct transmittance:
the proportion of a solar radiation, which goes straight through the glass without being absorbed. (See also solar properties)

Distance pieces:
sections of material used to space the pane of glass away from the upstand of the rebate in a frame, in order that an appropriate face clearance and an appropriate amount of sealant is present between the glass and the frame.

Double glazing:
depending on context:

Term often used for a replacement window

Is also used for secondary sash glazing

And for insulating glass units.

Double glazing unit:
an alternative name for insulating glass units comprising of two panes of glass.

Double window:
a window containing two panes of glass in the same vision area, but which are glazed separately, not formed into an insulating glass unit. It is sometimes described as secondary sash glazing.

Drained and ventilated glazing:
drained glazing where the rebates are deliberately ventilated so that external air circulates around the edge of the glass to assist in keeping the edges dry.

Drained glazing:
a glazing system in which any lodged water is channelled out of the rebates.

Driftwood™:
is the brand name for an old Pilkington patterned glass, which is no longer manufactured. It had an obscuration level of 5.

Drying agent:
another name for desiccant or molecular sieve.

Dual seal system:
the edge seal of a high performance insulating glass unit, which comprises primary seals between the spacer bar and the panes of glass and a secondary seal between two panes outside the spacer bar. Pilkington Insulight™ Units are made with a dual seal system.