how can i tell if glass is tempered or not?

Question

i need to know if a piece of glass i have that is 43" x 17" is tempered. i need to cut off a 3" strip so it will fit on the desk i built. i know there a couple techniques to detirmining if it is tempered or just heat treated but i just cant remember any of them plus i'd dont trust my limited knowledge

oh yeah its 1/4 inch glass from a coffee table and it doesnt have a lable or logo anywhere on it saying if it is tempered

Answer 1

Tempered glass is usually less flat than untempered float glass. If you look at the piece at a low angle, you may see a slight wave to tempered glass.
The best way to tell is to use polarized film. It's about 1 mm thick and flexible. This works best with sunlight. Bend it around the corner of the glass so that part of the film is 1/2 inch in front of the glass and the other part is 1/2 inch behind the glass. When you look through all three layers (film, glass, film) you will see a rainbow pattern coming from the corner of the piece of glass.
You could also try polarized sunglasses. If you look at the piece of glass while wearing them, you might see various rainbow patterns in the glass, obscuring your view. This is why polarized lenses are not recommended for driving; the side windows on cars are tempered.

Answer 2

tere will be writing in the bottom corner ( or a corner ) saying so !
tempered scratches easily!

Answer 3

Thankyou everyone for the answers