There are many different types of glass marketed as ‘security glass’ or ‘safety glass’. All have their advantages and disadvantages. Here we provide answers to the most frequently asked questions regarding glass, safety glass and security glass in general, and regarding our own products. Please contact us if you are unable to find an answer here to your specific query. If your work involves security, safety and property in any form, you are more than welcome to take part in our free seminars, where we go through and demonstrate the strengths and weaknesses of the various types of glass.
Hammerglass® is a durable and optically clear polycarbonate sheet, 300 times stronger than glass – and virtually unbreakable. Hammerglass screens are coated with a hard layer of silicon oxide which protects against scratches and wear and tear. The surface coating also provides 99.96% UV protection, which prevents Hammerglass screens from clouding or becoming discoloured over time.
Polycarbonate (PC) is a tough, transparent thermoplastic of exceptional durability. Polycarbonate is marketed under the brand names Hammerglass, Lexan, Makrolon, Saphir and more. The difference between the various makes and brands of polycarbonate lies among other things in the purity and surface coatings of the sheets. Without a surface coating PC is easily scratched and will also begin to yellow within six months. Many surface coatings primarily provide protection against yellowing.
Plexiglas® is one of several brand names for the acrylic plastic polymethylmethacrylate (PMMA). However, in common parlance the term Plexiglass is very frequently (and mistakenly) used to refer to plastic sheets in general. Acrylic plastic is sensitive to acids, acetone and other solvents. Acrylic plastic can be distinguished from Hammerglass by the fact that, when prised or subjected to blows, it will crack - unlike Hammerglass which bends without any crack formation. Furthermore acrylic plastic will burn, whereas Hammerglass is self-extinguishing when ignited
Glass which prevents, or actively reduces, the risk of personal injury to those who come into contact with it is designated ‘personal safety glass’, or in practice, ‘safety glass’.
Classification EN 12600 and EN 356, P1A to P3A.
Glass which protects against vandalism, firearms, trespass, burglary, explosion and blasting, water pressure, electromagnetic radiation, X-rays, fire, noise and UV radiation is designated ’security glass’.
Classification EN 356, P6B to P8B.
Toughened glass is up to five times stronger than ordinary glass. When it does eventually break, it disintegrates into an infinite number of small fragments – as anyone who has dropped a sheet of Duralex glass on the floor knows. The fragments are not however sharp-edged, which is why toughened glass is used for the side screens of motor cars. The advantage of toughened glass is that it is relatively cheap and easy to install. The disadvantage is that toughened glass has to be ordered to size since it cannot be cut after toughening has been carried out, and this results in long delivery times. Nor is toughened glass particularly difficult to penetrate. A light blow with a sharp object is often sufficient to break the pane.
Laminated glass consists of two or more glass sheets which have been bonded together with a plastic film. It is also sometimes erroneously referred to as ‘armoured glass’. Laminated glass can be produced as a very thick sheet, which together with the extremely tough interlayer makes it difficult to penetrate – or even, given sufficient thickness, ‘bullet-proof’. However, panes incorporating laminated glass are very expensive to buy and, what is more, difficult to install. The main disadvantage, though, is that laminated glass – as distinct from Hammerglass – cracks easily (even though it may hold together in one piece), which renders it an expensive material to use in exposed environments.
Ordinary flat glass can be laminated with a safety film on one or both sides. The major advantage of safety lamination is that it is an inexpensive way of making an ordinary glass pane more resistant to knocks and blows. The safety film also prevents glass splinters from being thrown around when the pane breaks up. Application of the safety film can be performed without the glass itself having to be replaced. However, the safety film does not specifically render the pane itself that much stronger. The pane will break under a load which is not that high, and will then have to be replaced (and a new film applied).
Bullet resistant glass (bullet proof glass) consists of several glass sheets laminated to resist the power of a bullet. The glass packages often become very thick - 5 cm or more - and therefore also very heavy.
Classification EN 1063, BR1 to BR7.
Unfortunately, many thieves have learned how to remove anti-theft grilles and roller shutters. If a strong rope is attached to a vehicle bumper or tow bar, the anti-theft grille can then be pulled away. Thus, apart from obscuring the view into a shop or display window, anti-theft grilles have in many cases given the shopkeeper or store manager a false sense of security.
Hammerglass unbreakable glazing solutions are available in all the security and safety classes up to P8B, which corresponds to the highest security class for anti-theft grilles and roller shutters. Hammerglass Ballistic Protection is certified in classes BR1-NS, BR4-NS and BR6-NS, Hammerglass Explosion Protection in classes EXR1/EXR2.
Normally, window glass may crack for a variety of reasons. If the glass is incorrectly installed, or if, for example, a screw head lies against the glass, then crack formation may occur. With this type of crack formation, cracks typically grow at irregular angles from the edge of the glass. Contact your installer if such cracks arise.
Thermal cracks may arise if the window glass becomes considerably overheated. A thermal crack always proceeds at right angles from the edge of the glass, in contrast to mechanically caused cracks which are formed at irregular angles. Contact your installer if such cracks arise.
The Glazing Installation Committee MTK (now ‘Glascentrum’) is a committee within the Swedish glass industry organisation, the aim of which is to ensure that glazing is correctly installed.
The Swedish Flat Glass Association is an interest organisation which includes manufacturers, finishers and trading companies within the Swedish flat glass industry.