tempered or not ?
 

how can i tell if i have tempered glass or not ? i got a tank that was custom built for a bar but i want to drill it and don't want to crack it and have to toss it , so is there a way to tell if it is tempered or not ? i know one way but it may end badly :)

take a polerized filter for a camera and look at the edge if its blackish its temperd... polerized sunglasses will work too.

If you have the right light and you wear polarized sunglasses you can also see a diamond shape cross hatch pattern to the glass if it's tempered,

I also believe that if it is tempered the diamond bit will simply slip, and not cut at all.

False, it will cut and shatter the glass. You can use polarized lenses but as far as I know you need two, one of each side of the glass. If you look through both filters you should see a spider web pattern if it's tempered and nothing if it's not.

Chances are it's not tempered glass, custom tanks are not usually tempered as it is almost always cheaper to use thicker glass over tempering. If you can supply the dimensions and glass thickness I can give an educated guess if it's tempered or not.

ok pannel sizes are ,base is 48 x 22 in front/back 32.5 x 48 in sides 20.75 x 32.5 in and thickness is 9/16 - 14 or 15 m i think if this helps , i will try the polar glasses , i have some of those , i fish :)

The glass thickness (15mm) would suggest the tank is not tempered, however since I didn't build the tank that's all I can say.

Best double check, perhaps you could contact the manufacturer?