When toughened glass was first introduced, it brought a lot of immediate safety advantages. The way in which untreated annealed glass breaks into large, sharp fragments had long been a safety problem. Toughened glass, on the other hand, shatters into small granular fragments, which fall to the ground without causing much harm.
Toughened glass was also an advantage in building design, especially as architects began to favour larger expanses of glass for its aesthetic qualities. However, it was the introduction of toughened laminated glass, a further advance in safety which allowed us to push the boundaries of design in the building envelope.
In the process of lamination, two layers of glass are sandwiched together using a PVB (PolyVinyl Butyrall) interlayer, which bonds the layers of glass together. This technique is normally used to combine two sheets of toughened glass, adding strength, safety and a wide range of functionality. Very quickly, architects saw the potential for introducing greater use of natural light and more open spaces in the indoor environment.
Lamination has allowed us to increase the size of the glass panel. With the considerable additional strength which lamination brings, we can now produce glass panels of several metres in height and width, and these panels can be joined unobtrusively, to produce a large expanse of glass which appears uninterrupted, allowing the architect full reign to their imagination.
Lamination can be used to introduce a host of other benefits too. By laminating two layers of toughened glass, safety can be taken a stage further, but so can security. If a panel of toughened laminated glass is damaged, the usual outcome is for the damaged section to stay in place. Most of the glass fragments are held in place by the interlayer to which they are bonded, so although the appearance of the glass may be marred, and the panel may become bowed or misshapen, it will usually stay in place. This not only protects the building’s users from coming into contact with shards of glass, it also helps to preserve the integrity of the external envelope. The damaged area may not even need to be boarded over before the glass panel is replaced, as there is no breach of the outer surface, as there would inevitably be with non-laminated glass.
This security aspect can now be enhanced still further, by laminating specially processed security glass with specialised interlayers which when used together, these form a high security glass which will withstand multiple blows from heavy objects or weapons. High security glass either prevents the external envelope from being breached altogether or extends the time that it would take to breach the glass panel sufficiently to deter the would-be intruder. Laminated security glass can now pass the standards for EN356 manual attack resistant glass. As a result, high security laminated glass is now commonly used in applications such as shop fronts and also inside the retail outlets in jewellery counters or to protect bank employees.
High security and ballistic resistant glass are helping us to design crime out of public buildings, deterring the use of firearms and ram-raiding by criminals. Processing techniques are such that we can also produce laminated glass which passes the tests for ISO 16933:2007, which governs the standards for blast resistant glass, which means that we can now construct buildings to be more resistant to terrorist attacks, without having to compromise on design qualities. This type of blast resistant glass is now increasingly specified for use in airports and rail stations.
We can also use interlayers to introduce some other properties to glass. Depending on the interlayer used, we can add sound attenuation. This can benefit those outside the building, by muffling the noise of a manufacturing process, but it can also help to provide a more tranquil indoor environment for the building’s occupiers, whether in an office or a domestic setting.
It doesn’t have to be either or; we can use interlayers to create sound attenuation with high security or to introduce a few other features such as privacy. Seclusion can be either permanent or temporary. One of the most popular advances in interlayer technology in the past decade has been the rise in use of the switchable interlayer. A switchable privacy layer allows the glass panel to be either transparent or opaque at will, allowing occupants to admire the view if they wish, but also to enjoy privacy. The interlayer is controlled by a small electric current. When current is passed through the interlayer, particles inside it line up to allow light to pass through and the panel becomes see-through. However, when the current is switched off, the particles in the interlayer align randomly, so that light can no longer pass through, making it opaque. Thus, the glass panel can be clear or opaque, quite literally at the flick of a switch.
Interlayers can also be used to introduce colour. This is a favourite with architects who like to provide a completely white interior, but to introduce a wash of colour as the light shines through the translucent coloured interlayer. This process can be used to incorporate corporate colours in commercial settings, and company logos can also be inserted during the laminating process. Opaque coloured interlayers can be used, or we can back-paint individual panels, to introduce colour blocking. This is increasingly popular in public buildings such as train stations, libraries and hospitals.
Fire safety is essential in many domestic and public settings, and for this we can now use laminated fire-resistant glass. Fire resistance is assessed in accordance with the amount of time that it can delay the spread of fire and rating given for glass than can pass the 30 minute or 60 minute tests. Fire resistance can also be combined with other properties such as security, sound attenuation or privacy.
Glass processing technology has advanced by leaps and bounds in the past decade and, thanks to the use of specialised interlayers, it is now possible to provide a tailored solution for almost any application that you can imagine. Given that glass is also a product with an exceptionally long lifespan, one of the oldest building materials on the planet is also destined to be one of its most sustainable.