Ordinary glass, also known as annealed glass or float glass was the most common form of glass available before the introduction of safety glass. Due to the increasing incidence of injuries caused by ordinary glass, most buildings today need to comply with current standards that require safety glass to be installed in high risk areas subject to human impact. There are three main types of safety glass, wired reinforced, toughened float & laminated glass. The most important characteristic of these products is that if broken, it does not shatter or splinter into large dangerous pieces, therefore minimising the risk of injury caused by broken glass.
Wired reinforced glass is classified into two broad groups, Clear plate and Figure Roll wired reinforced. Although both types are classified as Grade B safety glass, the industrial appearance has resulted in its limited use in recent times.
The figured roll variety was available in various colours and patterns, however a decline in popularity has seen the demise of a majority is these products. Domestic shower screens along with saw tooth roofs and factory windows in commercial properties would be the most common application for this glass today. A combination of other superior products entering the market and the ease of fracture due to thermal breakage and also expanding rusted wire could see the future of these products being reserved only for replacement of existing installations.
The fact that Clear Plate reinforced glass is considered to be fire rated may be the only reason for its future in the market place. While also suffering from the problems outlined about Figure Roll wired reinforced glass, when subjected to heat and fire it remains in position after breakage, preventing flames penetrating the building. Although there are other fire rated products available Clear Plate could remain as an economical option for fire doors in domestic or commercial properties or other fire rated applications.
Laminated Safety Glass is the most commonly used safety glass for domestic and commercial buildings. Laminated glass consists of two or more sheets of annealed glass or occasionally toughened glass, which have been bonded together with a PVB plastic interlayer. An extensive range of size and thickness are available, however the most regularly used products are 5.38mm, 6.38mm, 8.38mm, 10.38mm or 12.38mm laminated, in either clear, grey or bronze annealed laminated.
The most important characteristic of laminated glass is that when broken the PVB interlayer, which is sandwiched between the two sheets of glass, holds the glass together preventing large dangerous pieces of glass from falling out. Other features of laminated glass that have increased its popularity include, prevention of 99% of transmitted UV light, greater sound insulation properties and improved security that discourages entry by criminals or intruders.
Although laminated glass meets all of the safety requirements to conform to current standards, it is necessary to use toughened glass in certain applications. If broken, toughened glass fragments into hundreds of small harmless pieces. Whilst this is an important safety feature, thermal resistance and increased strength of up to five times that of annealed glass is the main reason for its use. Common applications of toughened glass include, frameless assemblies, shower screens, cooktops, splashbacks and semi frameless balustrades.
The down side to toughened glass is that during the toughening process the glass takes on a slight corrugated distortion that is visible on close inspection. Another problem is that once the glass is toughened, the glass cannot be cut or altered in any way. Therefore, each panel is cut and processed to create a custom made product that in most cases cannot be used in any other location. In addition to this, when toughened glass breaks in most cases the entire sheet disintegrates leaving an open path, minimising its security and safety benefits.