Advancements in the production of thin glass are permitting entirely new applications in architecture and broadening the performance spectrum of glass and glass panes.
The benefits of thin glass lie in its material and constructional qualities, as well as its low weight in combination with other glasses, such as multiple insulating glasses.
Lighter triple glazing
Thin glass is being used more and more for the middle pane in triple glazing, where it allows a clear reduction of thickness and weight. A pane structure comprises an outer float-glass pane (4mm in thickness), a semi-tempered middle pane (2mm) and another float-glass pane on the inside (3mm). Compared to conventional glazing (4-12-4-12-4), this combination reduces the weight from about 30kg/m² to 22,5kg/m², something that is particularly beneficial in refurbishment projects.
But thin glasses do not only reduce weight, they also excel with their combination of breakage resistance and high flexibility, which allows specific customisations. Moreover, they permit new and variable options in shape and design, as it is possible to add specially treated coats to thin glass, for example through grinding or screen printing.
In addition, thin glasses are used to cover a wide range of applications where polymer solutions have limits, such as in the coating on solar panels. Compared with a plastic film, glass is far more heat-resistant, keeps its shape, is gas-tight and has outstanding visual qualities.
Other forward-looking applications include integrated functional coats such as organic photovoltaics (OPV), where energy is harvested via windows or skylights, and switchable polymer-dispersed liquid crystal (PDLC) coatings. This technology permits the creation of cloudy, opaque viewing guards which only become transparent under an electric current. One specialist in this type of technology is the Austrian company LiSEC, whose vacuum coating process with diffusion-proof edge seals also protects functional coats from humidity and environmental impact.
Thanks to thin glass technology, curved glasses too may well become increasingly established in architecture. Tempered thin glass can be bent into the desired shape on site, either through cold bending or installation bending, and can then be used as single glass or as a coat. It is an inexpensive alternative to hot bending at the factory. Furthermore, cold-bent glass has excellent visual qualities, due to fewer distortions.
How thin is thin?
While in construction and architecture glass is considered thin if below 3mm, with virtually no reasonable or practicable use for thicknesses below 1mm, special manufacturing processes are now available for the production of ultra-thin glass films which at 25μm (0,025 mm) are even thinner than a human hair or razor blade. And despite its extreme thickness, it is highly resilient and scratch-proof.
This kind of ultra-thin glass is typically used in the automotive and media industries for example, where flexible thin glass is opening up new innovative options in virtual, mixed and augmented reality, but it is also producing new qualities that can be extended further in the manufacturing of glass.
How is it made?
The manufacturing of thin glass starts with molten glass which is passed through rollers and then drawn upward or downward from a tank in what is known as an up-draw or down-draw process. It is then left to cool down on the production line as a film with the required thickness, ranging from 25μm to 10mm.
Apart from these two methods, thin glass can also be produced with different specifications, using overflow or micro-floating processes. But since minimal thicknesses for the construction industry are commonly around 1mm, thin glass for architecture can be produced under a conventional floating process.
However, no matter the method used, the properties of thin glass are ultimately determined by the formula of the molten glass, which differs from one manufacturer to another and is usually a well-guarded trade secret.
Full thanks and acknowledgement are given to Glasstec and Messe Düsseldorf for the information and images provided. This article was originally written by Claudia Siegele, technical journalist and author of books on architecture, civil engineering and energy-efficient construction.
Caption: Cold bending makes it possible to place curvatures on glass immediately before installation.
Courtesy of Messe Düsseldorf/Lisec Austria GmbH
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