The float glass process was invented by Pilkington, and the first float line in Australia was commissioned in 1972. CSR building products purchased the Pilkington Australia business in 2007 and continues to both invest in the process and set the world standard for the production of high quality float glass.
Glass is manufactured by melting sand, soda ash, dolomite and limestone together and produces a continuous glass ribbon up to 3660mm wide. This flows from the furnace and ‘floats’ over a bed of molten tin. It is then carefully cooled to anneal the glass – a process which modifies the internal stresses enabling it to be cut and which maximises its potential mechanical resistance.
The float glass process is renowned for flatness and optical clarity. It is available in clear, toned, high performance toned, ultra clear low iron glass and Low E pyrolitic coated. Viridian installed a CVD coater to the float line, which enables online Low E coatings to be applied whilst the glass is in its molten stage of production.
This involves embossing a pattern into the glass during manufacture by passing the semi molten glass through a set of rollers prior to annealing. One side remains smooth whilst the texture is applied to the other side. A square wire mesh can also be included (refer to page 72 for range and sizes).
Insulating glass units
Also known as double glazed units, where two or more panels of glass are bonded to a perimeter spacer, either a metal or thermoplastic spacer, (TPS). Either air or argon gas fills the space between the glass panes. Their primary benefit is insulation and solar control. Most types of glass can be incorporated into an insulating glass unit.
Laminated safety glass
Comprises two or more layers of glass permanently bonded together with an interlayer or resin. If broken, the interlayer is designed to hold the glass together. Virtually all glass types can be laminated and the thickness and type of interlayer can be varied to provide safety ballistic, bomb or physical attack resistance. Normal laminated glass can be cut and further processed.
Toughened safety glass
Float or DécorPatterned glass is placed in a roller hearth toughening furnace. The glass is heated then rapidly cooled, resulting in the glass retaining high compressive stresses. Fully toughened glass is four to five times stronger than ordinary glass and if broken forms small granules. Heat strengthened glass has a lower residual stress and is two times stronger than ordinary glass. It is not a safety glass and if broken it forms large pieces. Toughened and heat strengthened glass cannot be cut and both are resistant to high differential temperatures (180–250°C).
Toughened laminated glass
This is the optimum in safety glass. Each piece of glass is toughened to provide superior structural strength when compared to annealed glass. These pieces are then bonded together using either PVB or resin as the interlayer medium, to ensure if the glass breaks the pieces are held together by the interlayer.
This family of high performance glasses consists of permanently bonded microscopically thin layers of metal oxides. There are two types of coating technology used in glass supplied by Viridian.
On line, or pyrolitic hard coated. These coatings are produced by depositing a metallic oxide gas chemical vapour deposition (CVD) during float glass manufacture. This process produces extremely durable coated products that can easily be handled, transported and processed. These products typically combine Low-Emissivity and solar control, and can also provide a wide range of properties from low reflection to self cleaning. Viridian has installed a CVD coater to its float line in Dandenong, which allows manufacture of a range of Low-Emissivity glass to meet the growing demand for energy efficient glass. Viridian’s local production will mean we can meet market demand for prompt supply and flexibility.
Offline coating. The Airco or magnetron sputtering uses high-grade glass that is placed in a series of vacuum chambers and coated with atoms of alloys such as silver and titanium. The properties of the metals provide solar reflectance and Low-Emissivity.
Coated glasses can be toughened, laminated or incorporated into an insulating glass unit. Under certain light conditions a small degree of haze may be apparent.
High quality float glass is backed with silver and protective coats of baked enamel paint. It can also include a vinyl backing for safety.
Screen printed glass
Uses ceramic paint that is screen printed and permanently fused to the toughened glass surface. A broad range of colours and designs is available.
Float glass is heated to its softening point and slumps into a mould that has a custom design providing a deep DécorPattern.
Glass designed to resist physical attack, ballistic and bomb blasts. These products are specialist laminates that use multiple layers of glass and rigid interlayers depending on the resistance required.
Self cleaning glass
Used for exteriors. The glass incorporates a pyrolitic coating that dissolves dirt (photo activ) and sheds water (hydrophilic) using natural UV light and rain.