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I think I've read somewhere, maybe here on this forum, that tempered glass can not be sandblasted. Am I correct? A local commercial glass company tells me that tempered glass can be sandblasted.
I say the glass has to be sandblasted before tempering. Any advice on this issue is appreciated. Thanks.

lohman wrote:I think I've read somewhere, maybe here on this forum, that tempered glass can not be sandblasted. Am I correct? A local commercial glass company tells me that tempered glass can be sandblasted.
I say the glass has to be sandblasted before tempering. Any advice on this issue is appreciated. Thanks.

You can FROST it after tempering, but if you want to carve it, blast first, then temper. Brock

Thanks Brock,
My guess is that the frost does not compromise the safety feature of the glass? Also at what depth of blast is it considered carving?

lohman wrote:Thanks Brock,
My guess is that the frost does not compromise the safety feature of the glass? Also at what depth of blast is it considered carving?

Well, you must have compromised it somewhat by blasting into that skin. Carving, on tempered glass, is when it goes bang! Actually, I would say that anything other than a surface frost on tempered is asking for trouble.

That's what I thought. I think my project can be made with laminated safety glass and I can do the piece minus the big bang.
Thank you, Brock.

PPG recommends not blasting any deeper than 10% of the glass thickness if it's been tempered.

Tony

My experience has been that there's tempered and then there's tempered...sometimes you can go 1/32" to 1/16" deep and be ok. Some glass explodes if you make 3-4 frosting passes over it. The problem is...you don't know which is which when you start out. I'd recommend learning shading...it will give you the look of carving with no physical depth

My personal experience has taught me to not even attempt any carve on tempered whatsoever. The properties of the glass itself are WAY too tempermental for carving.
Wonderful effects on tempered can be achieved by surface etching with shading techniques.
It's always wise to talk the client into safety laminate if you can, especially when you're not confident. Sometimes it's a given for tempered - the door has been bought with the tempered panel already installed for instance. The client wants obscurity. If you only have the tempered to work with, well then, that's all you have. Just remember the tempermental properties. Tempered = tempermental.
Sincerely, Nickie

I've never blown a piece of tempered, but I avoid being too aggressive with the depth of my etch regardless of what PPG says. I've carved 1/8 of the way into glass prior to tempering without a problem in the tempering oven... but even then I'm apprehensive about going too deep.

Tony

Thanks again everyone. You've given me some valuable advise and info.
The laminated safety glass is probably my safest approach.

We carve on 3/8" and 1/2" tempered glass all the time and have never blown a piece. I wouldn't try it on 1/4" though.

E

We carve on 3/8" and 1/2" tempered glass all the time and have never blown a piece.

but is the glass still strong or is the safety factor compromised?

I haven't ever had one break once it was installed and never had any refused by inspectors. I imagine if it received a hard blow to a spot where it was cut the deepest it might blow, but so far it hasn't happened to any of our pieces. We will use laminated glass whenever possible (when edges will not be exposed) also 3/8 and 1/2, not because it is stronger than the carved tempered but because if it breaks, the opening (doors or windows) will still be secure. Carved 1/4 lam is very weak. We've had several of those get broken by angry teenage boyfriends.

I've been told that signs painted on 1/4" tempered glass will weaken it as does rain while the surface is completely wet. Tempered glass is most vulnerable on the edges and corners.

E

Once you scratch the surface of the tempered glass, you probably weaken it by a factor of about half. Tempering makes it 5 - 7 times stronger.

I have frosted a pattern on tempered glass with no mishap.

Codes do not deal with this at all, so it is permissible according to code.

Thanks Bert and Ellen for the very helpful and informative comments.

I should research my local building codes.
And the tips about wet tempered glass and the relative weakness of 1/4" laminated glass is very much appreciated.

Do either of you write disclaimers into your contracts? I'm thinking maybe I should.