Motor vehicle windscreens are made up of laminated glass. This means that there are two layers of glass with a very thin film between them. This film holds the glass together in the event of it being damaged (figure 2). The side windows, and as a rule, also the rear windscreen, are made of tempered, single-layer safety glass (crumble-glass). Although it is generally more sturdy because it's a 'hardened' glass pane, it can however, not be processed in any way or in fact, even be cut, this in contrast to laminated glass.
Accident prevention 1
In the event of damage to crumble glass, first of all the remaining glass pieces must be carefully removed (figure 1). Safety glasses are of paramount importance here, because the fragments must be not only be vacuumed up, but also, by careful scraping with a large duster, be removed from all corners of the car body. Moreover, parts of the pane may still stick to the metal body-work and others may have disappeared into the upholstery, e.g., in the boot lid. In a nutshell, there can always be glass fragments flying around, therefore, the safety glasses.
Accident prevention 2
Nowadays, there are also motor cars which have air-bags built into the casing of the A-pillars. At this point, those without the necessary knowledge, should keep their hands off! An exploding air-bag, during the work is no fun at all.
The removal of the windows found in older cars, is the easiest, because these are not yet bonded, but mounted in solid rubber sealing lips. They also already have a self supporting effect, although this is only really achieved with the bonded window. One can recognise them by the silk-screen printing on the edges, and also not only do they often cover larger parts of the body-work, they prevent the penetration of ultra-violet light-rays, which over a period of time, would otherwise attack the adhesive by removing the softening agents.
Thus, whereby in the case of bonded windscreens a particularly sharp wire is used (picture), the screens of older vehicles can be removed by simply cutting out the outer rubber layer with the tool shown on the far right in the picture. Of course, before the actual cutting out and/or removal there are often a number of parts which have to be dismantled. Thereby, one should make sure that any screws can be easily turned out and that sometimes, special care must be taken.
It is advisable to remove any parts directly bordering on the windscreen, even though the manufacturer doesn't necessarily recommend that you do so. When exchanging of windscreens in vehicles once installed by the factory, (e.g., in campers), problems can arise. In addition, any installations carried out by the owner, e.g., thin wires which have been laid between the dashboard and the windscreen must also be carefully removed beforehand.
The wire is only applied after careful consideration. To remove the window, the pulling-wire is threaded through at (almost) any point from the outside inwards and clamped using the pulling and holding tools, (figure 3 centre and left) with a clamping screw. While one person holds the wire tightly inside the car at a certain point, the other pulls the wire step by step around the outside, until the window is free. Earlier used methods of heating the wire with electricity and/or the adhesive tape of the window are unusual nowadays. 12/14