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I have a full wall vanity mirror (70" x 42") in my bathroom wall. I need to drill some holes through it in order to install a vanity light. I realized that if the mirror is made from tempered glass it might shatter completely if I try to drill on it. The mirror probably is construction grade installed originally when the house was built in 1988.

Is there any way to tell if a mirror is made from tempered glass or not, without breaking it, and assuming that there are no "tempered glass" labels anywhere?

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up vote 7 down vote accepted

First really look for the watermarks. These are usually ultrafaint in a corner. They could even be upside down.

Second look for any chips on the edges. If there are chips it isn't tempered.

Third if you need the hole just drill it. Use the smallest bit you have to start and work your way to the size you need. Wear gloves but putting a tiny hole in tempered glass will probably cause a shatter but probably not the whole sheet. There is probably a 1% chance this is tempered if that as a vanity has no code requirement for that and I don't know of builders willing to pay triple for no reason.

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Thank you! It ended up being non-tempered. I just went ahead with one of those wingIts drill bit and bore a hole. It does take time, didn't know glass was such a strong material! By the way, do you guys know of any other way to cut my way out to expose the fixture electrical box (that's my end goal). Do I have to keep boring holes, or is it possible to get some pliers and widen out the hole without cracking it? – Jose Cifuentes Feb 16 at 0:34
@JoseCifuentes - A roto-zip with a 1/4" tile blade in it, maybe. Not sure how well it's going to like glass though. – Mazura Feb 16 at 3:54
You don't need a big enough hole for the whole box. You just need enough for a few wires from your light to get through. 1/2" should be plenty. Please go up in small increments on your hole size. I have ruined a few mirrors in my life trying to instantly drill a 1" hole. So you should need to drill the 1/2" and then the holes to attach the light. Make sure the screws are not being supported by the mirror. – DMoore Feb 16 at 5:48
Work was done. I drilled holes for the light fixture, was a bit of tricky to drill them in the right place, but luckily I had created a template before mounting mirror. I made a 1/2 hole in the middle to pull the wires, and two smaller holes for mounting the light fixture. – Jose Cifuentes Feb 22 at 20:24

Most of the installed mirrors I've met in the course of my work have been non-tempered.

Especially since you can't find markings, I'd assume that it's not.

And really -- the worst that can happen is a cascade of smallish hunks of glass. Then you'll send out for some glass that's appropriate for your needs.

Wear safety gear and go for it.

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