What Is Tempered Glass?


Tempered Glass Detail

Tempered glass is regular annealed glass that has been processed by a controlled thermal process to increase its strength in comparison to annealed (untempered) glass. The glass is heated in a special oven almost to a liquid state and then cooled very quickly to create a hardened outside surface. The interior of the glass is cooled more slowly, to create a balance of internal stresses.

Brown tempered backpainted glass backsplash behind cooktop

Brown tempered backpainted glass backsplash behind cooktop

This internal stress causes the glass to be much stronger than annealed glass (fully tempered glass is generally 4 to 6x stronger than annealed glass), and creates the characteristic “nugget” breaking pattern and a greater resistance to thermal shock. Tempered glass must be fabricated fully with all holes, edging, and shaping done prior to tempering because of the internal stress. However, any non-ceramic frit coating (silver, paint, etc.) must be done after tempering due to the incredibly high temperatures in the tempering oven.



Tempered glass is more prone to breakage at the edge where the tensile stress is greatest.  When tempered glass is broken, it crumbles into granular chunks, instead of jagged shards. These nuggets of glass are less likely to cause injury, so some people refer to it as “safety glass”. The greater the surface stress, the smaller the glass particles will be when broken.


Avery Glass Gray Tempered Shower Enclosure

Fully tempered glass is often used in glass shower enclosures, glass doors and tables, backsplashes, shower walls, stair railings, glass storefonts and other architectural applications. It is often recommended for “pass through” applications where the back of the glass is not fully supported, or where the glass may come in contact with quick and extreme changes in temperature.

Eisner Design, LLC. New York area residence with playroom & workout room

Eisner Design, LLC. New York area residence with playroom & workout room


Ideal Uses of Tempered Glass: 

  • Custom shower door glass
  • Display case glass & mirror
  • Glass for railing systems (where applicable by code)
  • Storefront glass
  • Commercial entry doors
  • Tempered mirror in public restrooms
Public Restroom - Tempered Safety Mirrors

Public Restroom – Tempered Safety Mirrors

We are very excited to be able to offer tempering to our fabrication capabilities in addition to our water-jet cutting, edging, painting, and CNC fabrication. Keeping more of these processes in-house allows our customers to get product faster, with more control over the quality; without the risks associated with additional traveling and handling. Gardner Glass Products is fully certified in 4mm5mm, 6mm, 10mm, and 12mm glass thicknesses in a variety of glass types, including low-iron, tints, and acid-etched finishes.

So now that you know a little more about Tempered Glass, give us a call for your tempered glass needs! 1-800-334-7267


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