Glass and it’s Properties

The process of manufacturing glass is simple. Mix three minerals then heated until they become one. These three substances are;                                                                                                                                                                                                                                                                                                        1) Sand which gives silicon,                                                                                                                                2) Calcium carbonate (limestone) that stabilizes the glass and will not dissolve in water,                           3) Sodium carbonate (soda) which lowers the melting point of the sand.

In these components, depending on how the glass is to appear, other ingredients are added such as various metal oxides. In this way the glass gets coloured. If for example, iron is added, the glass becomes brown or green. When cobalt or chromium is added, the glass becomes green or blue.NOTE: Good quality glass should not have any image distortions!

Categories of Glass in Window Frames

The glass panels used in windows play a very important role in the final performance of the construction. There are many choices in types of glass and each option depends on the position of the frame.

  • Energy glass (low-e)
  • Double glass (conventional or energy)
  • Triple glass (conventional or energy)
  • Triplex (laminated)
  • Security (toughened)

Single glass (conventional)

Energy Glass (low-e)

The energy glass or low emissivity glazing (low-e) at one side of the surface has a special coating which acts like a mirror in the infrared and ultraviolet portion of the electromagnetic radiation. As a result there is reduction of thermal radiation of the sun passing through the glass. At the same time there is no escape outwards of thermal heat from the interior.

This coating consists of a very thin transparent film. Energy glass are never used alone only as double or triple.

It should be noted that the use of energy glass greatly reduces fading of colour (curtains, furniture ...) from the sun's rays. It also is energy efficient, saving us money!

Double Glass

Double glass consists mainly of two panes which are held separate from each other through space between them. Between the two glass panes is dry air. An aluminium spacer is placed between the panes, called silicates, and this absorbs moisture. If you choose a larger spacer size, then this becomes a more highly insulating construction. Double glass is made with a special heated glue.

Also, with double glass we can do combinations of glass:

  • Single conventional - spacer - single energy
  • Single conventional - spacer - triplex (laminate)
  • Single energy - spacer - triplex (laminate)

It is worth noting that in combinations with energy efficient windows, the space between the glass can be filled with gas (argon) thus increasing even more highly the insulation of the windows !

Triple Glass

Triple glass is the extension of the double plus another spacer and glass.

The combinations of glass are:

  • Single energy - spacer - single conventional - spacer - single energy
  • Single energy - spacer - single conventional - spacer - triplex
  • Single conventional - spacer - single conventional - spacer - single energy
  • Single conventional - spacer - single conventional - spacer - triplex
  • Single conventional - spacer - single conventional - spacer - single conventional

Triple glass has much better results than the double. Also, the frame in which triple glass will be placed should be enhanced for support according to weight ratio.

Note that, here also, combinations with energy can be done using gas (argon).


Triplex glass is the result of combinations of two or more panes. The material that joins membrane is transparent or translucent or coloured. With this combination the glass is very impact resistant, but even if it does break it will not collapse as it is retained by the membrane. When we look at their surface, they seem like single glass. This glass is usually used in frames 3 + 3 or 4 + 3.

Triplex glass type 3 + 3 + 3 (three windows / two membranes) are characterized as anti-vandal and triplex structures 5 + 5 + 5 as bulletproof.


This glass is "baked" in an oven to toughen. Breakage is rare but even if it does break it crumbles into small pieces without causing injury.

Security glass is used in special constructions such as glass doors, windows, etc.

Single Glass

Single glass is known as "conventional" glass. It is used in locations where cooling or heating are not necessary and the thickness of this glass is between 4 - 12 mm.