Glass:
Glass types

Glass as used in the double-glazing industry:
There are so many types of glass used in the double-glazing industry you simply would not believe it! Fortunately, in the home only a small number are used in the normal way, and so I will simplify this page by discussing those commonly used for domestic and mostly double-glazing locations. For the technically minded who may be interested I have provided a link to Pilkington at the bottom of the page for a much more comprehensive list of types and their respective properties.

Types of glass commonly used for domestic locations and double glazing

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. This type of glass can still be seen in older houses and buildings today. It is also what is known as 'greenhouse glass', normally '24-ounce' in weight (now 3mm in thickness).

Float glass:
A new process of floating molten glass on molten metal (tin, I think) was invented (by a Mr 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 ordinary glass as used in most windows today. Although surprisingly pliable and easy to cut when new, after a few years this annealed glass starts to become more brittle, and cutting say 20-year-old glass is noticeably more difficult. When this type of glass gets broken it can be extremely dangerous, with shards as sharp as a razor. I have seen people cut themselves on glass by handling it too gently, thinking this is the best way, but it is not, it gentle handling just makes it more likely to slip. Always remember to have a firm grip on glass when handling it so that it cannot slip. When I show people how to handle glass with bare hands I get a piece of glass and smack the sharp edge: I receive no cut. I then explain that if I ran my hand along the sharp edge of the glass I would have a nasty cut. 
Do not try this yourself! And never handle glass with bare hands!

Obscured glass:
Available in a variety of patterns with different levels of obscurity, most of which can be toughened.

Go to my 'safety glass' page
Double-glazed 'misted-up' sealed units
Do double-glazed sealed units have a vacuum?
About double-glazed safety glass
Double-glazed sealed units - manufacturing techniques
Double-glazed air gaps and insulation
Why did my sealed double-glazed unit explode?
Brewster's Fringes in my double glazing