Annealed Vs. Tempered Glass, What is the Difference?

Tempered glass is harder and stronger than annealed glass. When tempered glass breaks, it breaks into small pebble shaped pieces like a car’s side glass after an accident. This is why it is often called safety glass. Tempered glass is annealed glass that has been heat treated to harden and strengthen it.

Tempered glass is more expensive than annealed glass because of the added heat treatment processing.

In general, heat treated or tempered glass is four times stronger than annealed glass. Tempered glass cannot be drilled or cut without shattering. All fabrication needs to be done while the glass is in the softer, annealed condition. Annealed glass can be cut, drilled, notched and edge finished. Tempering is only done once the shaping and fabrication is complete.

Types of Glass

Annealed Glass, sometimes called standard glass is a softer glass that has been thermally treated and then slowly cooled to relieve any internal stresses. Annealed glass tends to break into longer, jagged shards which can cause significant injury. It is generally used when strength or safety are not concerns but cost is.

Tempered Glass or toughened glass is manufactured through a process of extreme heating and rapid cooling, tempered glass is much harder and stronger than normal glass. Another benefit of tempered glass is the ability to stand up to moderate heat (470°F).

Laminated Safety Glass takes the idea of safety glass a step further. Laminated safety glass is crafted by adhering two pieces of annealed glass together by a vinyl layer. The vinyl layer holds the glass together if the glass is broken or impaled.