Toughened glass, sometimes referred to as “Tempered glass“ or “Safety glass”, is very simply a stronger version of the standard glass that is used in most windows around the home. It is used in areas where greater strength or safety is needed, for example, in doors, windows near doors or windows at low levels.
To toughen glass, we heat standard “annealed” or “float” glass in a furnace to around 650 degrees and then rapidly cooled. This process changes the structure of the glass, making it around four times stronger than standard glass. The process also changes the break pattern of the glass. So, if broken, it shatters into lots of small pieces, about the size of a finger nail. Instead of a few large sharp pieces like the standard glass. Therefore, it is much safer to use in vulnerable locations around the home, such as in doors or low-level windows.
The normal thickness of toughened glass is 4mm, this is the same as the standard glass. In a double glazed unit you would have two panes of toughened glass, inside and out.
While Laminated glass, also known as “safety glass”, is used in vulnerable locations around the home. Sometimes, laminated glass is confused with toughened glass. This is a mistake, as the two differ in several important areas.
One of the most common uses of laminated glass is for car windscreens. If you have ever been unfortunate enough to experience a broken windscreen, you may have noticed that once smashed, the laminated glass holds in place and does not break into large, sharp pieces like standard glass or lots of small pieces like toughened glass. Both of these would be dangerous if you were driving. Instead, it remains intact long enough for you to have a replacement installed.
Laminated glass stays in place because it is made up of two pieces of standard glass. These have a thin, clear plastic interlayer sandwiched between them. The polyvinyl butyral (PB) layer bonds the two pieces of glass together. This means that even when it breaks, the fragments are kept together and intact in one sheet. The standard laminated glass is made up of two 3mm sheets of glass with a 0.4mm PB interlayer, making it 6.4mm overall. Normal toughened glass is 4mm thick. Generally, you would only have one pane of laminated glass in a double-glazed unit, normally the outside pane.
