How to really tell if glass is tempered or heat treated?

Hey guys, I’m new to window cleaning and while scratched glass is always a concern from what I’ve been reading it sounds like 90% of the time it’s only with temperd or safety glass ( if I’m wrong please educate me). So with that being said how do you know for sure if its temperd? I know it supposed to have a label etched on it but I would imagine that’s not always the case. So how do you know for sure what type of glass your dealing with?

Tempered glass will always have a stamp on it to that effect. I understand that some heat-treated or strengthened glass may not require a stamp, but I can’t confirm that from personal experience.
Building code in the US requires all doors, skylights, panes within 24" of doors, bathroom glass 5(?)’ or lower from the ground and glass on stairways 4’ or lower above the floor must be tempered. This may be off a little, others may have more exact info.
You can certainly find out more also by researching.

Hit them hard w a hammer if they shatter into a 2000 pieces they r tempered if they produce long sharp ex wife killing blades of glass they are annealed. Or u could just look for the stamp. All glas going to within 2 feet of floor, within 2 feet of a door , all bathroom glass if it’s within a certain foot from floor all needs to be tempered. But deffinatly start off w the hammer it’s a lot easier then Looking for the stamp.

here’s some info you may find useful regarding tempered glass and stamps

This brought tears to my eyes, I was laughing so hard!

Oh, and you won’t have to worry about scratching that one…

I always keep my sledge hammer on hand but every once in a while a customer gets mad when you test it out that way lol. Thanks for the info guys.

Where is [MENTION=14804]Gary Mauer[/MENTION] when you need him!

You could get one of these for $350. It’s a meter that will detect tempered glass.
There’s a picture on this gadget of an arm wielding a hammer - I guess everyone likes the hammer joke.
You could also use polarized sunglasses and look for quench haze. (I think you can google for an image to see what that looks like.)

If you need to know for sure, you’re going to have to invest plenty of time.
Better to get the client to promise not to hold you liable for scratches to tempered glass.

[MENTION=14804]Gary Mauer[/MENTION] Do you know why this is?

Bathroom windows with a tub or shower only have to be tempered.

The Fields Company - Glass Quality

The roller side is the side that touches rollers when glass goes inside a tempering furnace. If the rollers are contaminated with glass fines and other fabricating debris, that side ends up loaded with defects that cause scratching.
It’s useful to be able to figure out - after the fact - that only the roller side got scratched during scraping, because that’s a red flag for a quality problem.
In practice, if you’re trying to scrape only where you don’t fear fabricating debris, it’s not so easy to be sure.
Some of the tempering marks are inside the double unit, and hard to make out. The glaziers don’t necessarily face glass the same way, and don’t necessarily remember to put windows in the right location. (If glaziers accidentally put a 20x40 annealed window in the bathroom, that means there’s a 20x40 tempered window somewhere else in the house.)
The window maker might have used tempered glass from multiple sources that are not necessarily marked the same way.
Also, Caleb didn’t mention laser marking, which is becoming more prevalent. Laser marking can be done on either side.

Anyway, if you decide to try and protect your client’s glass from scratching by changing methods on tempered glass, you should include them in the decision and get them to sign a waiver, stating that they promise not to hold you liable for any scratched tempered glass.
(Even if they want you to ignore paint specks on tempered glass - if you’re using a scraper anywhere else, get a waiver signed)

I forget how to delete a duplicate post - so you guys must endure an oops!