The basic process for creating curved glass
All curved glass starts life as normal, flat plate glass. The process to turn it into curved glass is both highly specialised and time-consuming, hence curved glass can often carry a much higher price tag than flat glass.
Before the process can begin, precise measurements are needed for the particular job. A steel mould is constructed according to these measurements, shaped to the curve radius and dimensions of the end product.
The flat glass is then cut to size, and must be thoroughly cleaned and polished. Any rogue particles of dust or dirt could cause the glass to shatter during the bending process, so to ensure it is absolutely clean, a UV light is shone over the glass. This will highlight any small spots of dust that can then be cleaned away.
A mixture of detergent, clay and calcium carbonate is then painted onto the glass. This is to stop the glass sticking to the steel mould during the heating process.
Because steel heats up at a slower rate than glass, the steel mould is pre-warmed to around 480°C. The glass can then be placed on to the mould and loaded into the kiln.
The temperature in the kiln is raised up to 700°C, at which point the bonds between the glass’s silica molecules begin to loosen. This causes the glass to soften and bend, so it can take on the shape of the mould. This shaping can either be achieved through gravity alone, or can be assisted by a mechanical bending press.
The temperature in the kiln must be very carefully controlled at this point, as any variation in temperature across the oven would cause the glass to bend unevenly.
When the glass has fully curved to the mould’s profile, it is gradually and gently cooled over a number of hours. This slow cooling process prevents the curved glass from cracking.
The newly curved glass is then removed from the kiln, ready to be used in whatever application it is destined for.
Types of curved glass
Curved glass is available as standard annealed glass, toughened glass and laminated glass.
If the curved glass is to be toughened, these two processes will be done simultaneously. Instead of reducing the temperature gradually after the bending process, the curved glass will be rapidly super cooled.
This tempering process creates the centre tension within the pane of glass that makes it up to five times stronger.
Once glass has been treated in this way it can no longer be cut or drilled, so it can only be produced to order and measurements must be precise.
Laminating is a popular option for curved glass. This process is done after the glass has been curved, where two or more sheets of identical curved glass are sandwiched around a sheet of transparent laminate interlayer, then pressure bonded together.
This laminated curved glass can be cut or shaved for a perfect fit, so is frequently the preferred safety glass option.