Author:
Alice Brown
Date Of Creation:
23 May 2021
Update Date:
1 July 2024
Content
Toughened, or toughened, glass is glass that has been annealed to make it stronger, improve its heat resistance and prevent brittle breakage that can lead to injury. Such glass is used in entrance doors, shower stalls, fireplaces and grates, as well as other places where strength and safety are required. The glass tempering process is similar to tempering and tempering steel; in this article you will find a description of how to temper glass.
Steps
1 First, cut the glass to the desired shape. This must be done before tempering, as the glass can crack and shatter during cutting after tempering. 
2 Check the glass for defects. Cracks or voids can cause glass to break during tempering; if you find such defects, do not temper this glass. 
3 Sand the cut edges with sandpaper. This will remove any burrs and irregularities left after cutting the glass. 
4 Wash the glass. This will remove fine grains of abrasive left on the glass surface after sanding it, as well as dirt that can affect the hardening process. 
5 Preheat the glass in an annealing oven. Pieces of glass can be reheated by placing them in the oven in batches or one at a time. The oven temperature must exceed 600 degrees Celsius (1.112 degrees Fahrenheit), with the temperature commonly used in industry being 620 degrees Celsius (1.148 degrees Fahrenheit). 
6 Temper the glass by cooling it down. For this, the heated glass is blown with strong air currents at various angles for several seconds. With this intense cooling, the surface of the glass cools faster than the inner layers, which increases the strength of the tempered glass.
Tips
- Properly tempered glass must withstand stresses of at least 68,948 kilopascals (10,000 psi), but typically it can withstand 165,475 kilopascals (24,000 psi) without breaking. When destroyed, such glass breaks into small and, as a rule, rounded fragments. Annealed glass, processed by another method, withstands only 41,369 kilopascals (6,000 psi) and often breaks down to form large sharpened fragments.
- Tempered glass, when fixed, can withstand temperatures up to 243 degrees Celsius (470 degrees Fahrenheit). At higher temperatures, it softens. Holding at temperatures close to the temperature of its annealing for hardening leads to crushing and shattering of the glass.
Warnings
- Irregularly shaped tempered glass fragments can withstand loads from the wide end, but at the same time crumble under the same loads from the sharp ends.
