Below are the Types of Glass commonly used for Domestic Locations, and the Double Glazing Industry.

Sheet glass:

Many years ago glass for windows was drawn 'Sheet' glass, normally '32 ounce' in weight (now 4mm in thickness) which had noticeable distortion, and this type of glass can still be seen in older houses and buildings today. It is also what is known as 'greenhouse glass' normally '24ounce' in weight (now 3mm in thickness).

Float glass:

Manufacturing Process:

 
The term "float" glass derives from the production method, introduced in the UK by Sir Alastair Pilkington in 1959, by which process 90% of today's flat glass is manufactured. The raw materials (soda lime glass, silica sand, calcium, oxide, soda and magnesium) are properly weighted and mixed and then introduced into a furnace where they are melted at 1500° C. The molten glass then flows from the glass furnace onto a bath of molten tin in a continuous ribbon. The glass, which is highly viscous, and the tin, which is very fluid, do not mix so that the contact surface between these two materials is perfectly flat. When leaving the bath of molten tin the glass has cooled down sufficiently to pass to an annealing chamber called a lehr. Here it is cooled under controlled temperatures, until it is essentially at room temperature.

A new process of floating molten glass on molten Tin was invented (by Sir A Pilkington, working for Pilkington's Glass, but not one of the same family), which produced a far more distortion free product, and this is the everyday ordinary glass as used in most windows today.

Toughened (Tempered) Glass:

Four to five times harder to break than ordinary annealed glass, and if it breaks it does so safely by disintegrating into thousands of very small pieces with dulled edges (like car windscreens used to). In a normal thickness of 4mm, this is what is commonly used in most Sliding Patio Doors and Front and Back doors in the replacement industry today.

The other type of safety glass is Laminated, which looks much like ordinary glass, but has an almost indiscernible tint, which some customers think makes them look as if their net curtains are dirty! The slight tint is the result of the sandwich structure of Laminated Glass where two layers of 3mm glass are used with a tough plastic interlayer called polyvinyl butyrain (pvb). The combination of the extra thickness , now 6.4mm overall, and the plastic interlayer is what gives it the slight tint. Although Laminated Glass uses ordinary non toughened annealed glass, when hit hard enough the outer layer of glass may crack, but the broken pieces will adhere firmly to the interlayer, and so stop splinters of glass flying off.

Laminated glass:

Laminated Glass is a combination of two or more glass sheets with one or more interlayer of plastic (PVB) or resin. In case of breakage, the interlayer holds the fragments together and continues to provide resistance to the passage of persons or objects. This glass is particularly suitable where it is important to ensure the resistance of the whole sheet after breakage such as: Shop-Fronts, Balconies, Stair-Railings, Roof Glazing.

Production:

 
There are two types of Laminated Glass: PVB and Resin Laminated glass:

• PVB laminated glass is two or more sheets of glass which are bonded together with one or more layers (PVB) under heat and pressure to form a single piece.

• Resins laminated glass is manufactured by pouring liquid resin into the cavity between two sheets of glass which are held together until the resin cures.

Identifying Safety Glass:

All installed safety glass should be clearly marked with the British Standard test reference BS6206, with the letter L for laminated, and T for toughened, together with the company registration number of the supplier.