Glass is available in a variety of thicknesses. The thickness you choose depends on things such as the amount of exposure to wind (and the suction load on the surface) and the size of the sheet required. Most domestic glass is 4mm thick.
Sheet glass is generally available in three grades: OQ (Ordinary Quality) for general glazing, SQ (Selected Quality) and SSQ (Special Selected Quality). Modern sheet glass is of good quality, however one side is never completely flat due to the methods used in its manufacture.
Float glass is produced by floating liquid glass over a surface of molten tin. This results in a distortion-free sheet and can be produced in thicknesses of between 3mm and 25mm. Float glass is usually used for large picture windows and things like glass coffee tables due to its strength. It is available in a variety of finishes including tinted, etched, sandblasted and mirrored.
Patterned glass is used for modesty glazing in areas such as bathrooms. It is usually rough-cast, meaning it is smooth on one side and textured on the other. Patterned glass is not usually available in thicknesses above 5mm.
As the name suggests, wired glass is manufactured with a wire mesh embedded in it. This mesh acts to hold the shards together in the event that the glass is broken. Mesh glass is a recognised fire retardant and often found in fire doors. You can buy wired glass with either square or diamond pattern wire, in thicknesses up to about 5mm. If you plan to use wired glass, it is best to get it cut exactly to size when you buy it, as cutting later will be difficult.
Sheet, float and patterned glass can all be toughened to up to 5 times their original strength. This process not only makes the glass stronger, but also means that in the event of a breakage, the glass shatters into granules rather than sharp shards. Toughened glass is much more expensive than standard glass.
The manufacture of laminated glass involves sandwiching a layer of plastic film between two sheets of glass. The plastic sheet both helps to absorb impact (making the glass stronger) and holds the shards together if the impact is strong enough to break the glass.
Solar Control Glass
This specialised glass is most often used in offices and other commercial buildings to reduce heat, light and glare from sunlight. It is available in a range of colours and patterns, as well as in laminated form.