Toughened glass, and how it is made
The NSW Government’s page on toughened glass says the glass is made by heating it to a molten state at about 600°C and then chilling it suddenly with compressed air. That cooling makes the surface contract rapidly and form a rigid outer layer around the glass. The same page says toughened glass is commonly used in products like stovetops and hobs, cookware, tableware and shower screens. And Your Home notes that toughened glass can be used as safety glass as mandated in Australian Standard AS1288, and may be mandated in bushfire-prone regions.
What happens when toughened glass breaks
The NSW page describes the failure in detail. A break in toughened glass, such as a shower screen, can occur when a small chip or a weakening in the hard outer layer disturbs its surface tension, and the glass can burst inwards or implode without warning. When it implodes, it shatters into small blunt cube-like granules that are far less dangerous than jagged shards.
Two habits change the odds, in the same page’s account. Poor installation and maintenance increase the risk of toughened glass imploding, and the likelihood is greater if a moving part, such as an unframed edge of a pivotal glass door, is in close contact with another hard surface; an unframed edge that is rubbing should have the glass and door hinges adjusted immediately. The page also says the risk can be minimised if the glass and hardware, hinges and so on, are properly maintained and cared for, and that manufacturers often include a leaflet on how to care for the glass and hardware, which is worth following.
If you become aware of an unsafe situation or item, whether or not anyone has been injured, the NSW Government’s advice is to alert the supplier about the issue; a complaint can also be lodged on its website or through Product Safety Australia.
Laminated glass, and what it is made of
Your Home describes the two-sided nature of ordinary glass first: standard glass will readily break into long shards and small sharp slivers. Laminated glass has a plastic glazing layer, called an interlayer, which is adhered permanently between two sheets of that standard glass. The same page says this build lowers the danger of the glass breaking and, if it does break, holds all its shards in place so they do not come loose as dangerous shards.
The same page says where it is used: laminated glass is often used in the areas of a home most prone to injury from human impact, such as bathrooms, doors, around staircases and in areas close to the floor, where it meets the requirements of safety glass that Australian Standard AS 1288 mandates for those places.
The two, set beside each other
| Toughened | Laminated | |
|---|---|---|
| How it is made | Heated to about 600°C, then chilled suddenly with compressed air, so the surface contracts into a rigid outer layer. | A plastic interlayer adhered permanently between two sheets of standard glass. |
| What is described of a break | A chip or weakness in the outer layer disturbs the surface tension and the pane can burst inwards or implode without warning, into small blunt cube-like granules. | Where standard glass breaks into long shards and small sharp slivers, Your Home says the interlayer build lowers the danger of a break and, if the pane does break, holds all its shards in place. |
| What the code calls it | Both are the safety glass the code asks for at the places the code names: it asks for Grade A safety glazing material, with exceptions it sets out, and where it names the two itself, at an unframed door, it allows toughened safety glass of at least 10 mm nominal thickness or laminated toughened safety glass of at least 10 mm total thickness. | |
| What is asked of it | Marked in the form of either permanent etching or a label that cannot be reused once removed, as the code’s identification clause asks of safety glass. | The same marking rule. In kitchens, bathrooms, ensuites, spa rooms or the like, shower and bath glass included, where the glass comes lower than 2.0 m above the floor, bath or shower base, the code asks for Grade A safety glazing material in framed panels, and for toughened safety glass at least 6 mm thick in panels or doors with any edge exposed. |
One thing follows from the table, and it is worth saying plainly. The two come apart differently: toughened glass into small blunt cube-like granules, laminated glass with all its shards held in place.
Choosing between them
Where each is asked for in a home is the first guide’s ground: where the code asks for safety glass sets out the places the code names. If the window faces a bushfire risk, one of the pair comes up again in glass in a bushfire-prone area, where four states’ official pages are set side by side.
Neither guide picks for a particular window. The place a pane sits decides which rule reaches it, the mark on the glass is what a supplier can be asked about, and the maker’s leaflet is where the care of either glass is set out.