Engraving Tempered Glass

[Glenn Norton]

Have a customer that wanted to know if we can laser on tempered glass. Have never done it as far as I know. We have an Epilog CO2 maching. We quite a few acrylic and glass awards but not sure about tempered glass.

Thanks

[Bert Kemp]

The short answer is Yes you can engrave tempered glass. Some things to consider is what it will be used for after its engraved. I'm thinking it may loose some of its strength , so if put under a heavy load it might shatter.

[Rob Damon]

https://makerindustry.com/can-you-laser-engrave-tempered-glass-how-to-etch/

Sound like you can with a CO2 laser.

But and a big but. If the safety glass is being used in a building door, window, balcony rail, stair rail, office glass wall, I would consider carefully whether to do it or not.

The building code requires temper glass for a reason and if you lower it's strength and it fails and someone is critically injured or killed, you could on the hook for it.

If it is for purely decorated purpose and not be used in a area that it is mandatory by the building code, you maybe safe.

[Bert Kemp]

I think the guy that wrote that article doesn't know much about co2 lasers LOL

[Kev Williams]

ummm... I've never been able to "engrave" glass. And I've tried. Some of the glass I've ETCHED, I've gone over as many as a dozen times just to see if I COULD get a deeper etch. Not much else happens after the first pass. Had a customer (a stair company) bring me some miniature stair risers they molded from molten glass, they were about an inch thick both ways and 4" long. With all 80 watts of my Triumph I was able to melt the glass, turned out really cool. I tried that on some mirror tile... what I got was a million pieces of mirror tile to clean up, the glass basically exploded. Another test I tried once with mirror tile, I took a basic steel-wheel glass cutter and scored a line across 4" of one corner. On the opposite corner I laser scored a line. The scored lines look almost identical. I put the cut edge along a table and snapped the corner off perfectly. I put the lasered edge along the table and and the glass broke everywhere BUT the line. Fail!

Glass made with Borate is very resistant to C02 lasers. This jar I engraved many times at Cermark speeds, all I got was the slightly mottled finish you see-but after I gave up trying is when the fun began, as the jar sat on shelf, over time the surface of the glass started cracking, and all in one direction- 90° opposite the raster direction- which I found interesting...
451938
451937
I still have this sitting on a shelf, just to show customers that 'engraving glass is like a box of chocolates...' ;)
(I didn't know this was borate glass 'til after the fact)
-and don't you dare run a finger across it, some of those cracks run deep and those shards hurt!

So-- given my experiences with glass, I'd say that it's likely that tempered glass will etch okay, BUT- if for instance, the glass WAS a refrigerator shelf able to support eight 24-can cases of Pepsi, it would likely shatter under the weight of just ONE case after being laser etched. And what would happen after time, like my borate-glass jar, is anyone's guess. Might be worth getting some tempered glass for yourself to experiment with -?

[Mike Null]

I do a lot of tempered glass and generally do not agree that laser engraving degrades it. Can you cause degradation--yes, but not by engraving it using responsible settings.

[Rob Damon]

Mike, Visually you may not think it is degrading it, but would you really want to be at the middle of a law suit that a child shattered a piece that was engraved and got hurt?
Still practicing in the A/E field we have to sit through the legal seminars and sit in with code officials and have to justify modifications to UL tested material that has been modified without follow-up testing and the answer is no, don't take the chances. If this is just an ornamental thing, then it would most likely be fine but if it is for a real building and it is required by the code, checking with the manufacturer is best.

[Rob Luter]

Engraving will not "degrade" the glass or make it less safe. It can make it more prone to spontaneous breakage depending on when it's done. My workplace produces many millions of square feet of tempered glazing annually. We make it for both DOT and Architectural applications. It is all marked one way or another. We use grit blasters to etch, lasers to engrave, and also screen print. Ideally marking is done prior to the tempering process. Tempering places the entire exterior surface of the glass in compression. Disrupting the surface compression post tempering can create a weak spot that can conceivably cause breakage. That's why we mark first, then temper. If it breaks it will break into the same small pieces no matter how or when it's marked as long as it was properly tempered.

[Rob Damon]

Engraving will not "degrade" the glass or make it less safe. It can make it more prone to spontaneous breakage depending on when it's done. My workplace produces many millions of square feet of tempered glazing annually. We make it for both DOT and Architectural applications. It is all marked one way or another. We use grit blasters to etch, lasers to engrave, and also screen print. Ideally marking is done prior to the tempering process. Tempering places the entire exterior surface of the glass in compression. Disrupting the surface compression post tempering can create a weak spot that can conceivably cause breakage. That's why we mark first, then temper. If it breaks it will break into the same small pieces no matter how or when it's marked as long as it was properly tempered.

That is kind of my point. If the manufacturer does it before tempering and they are willing to provide the product with a listings, then that is one thing. Code officials will accept that all day long because the burden of failure falls on the manuf. and not the engineer/arch or code official. Once it leaves the plant, unless you can get a letter from the engineer at the manuf. plant say it is safe to engrave, then it becomes the liability of the engineer/arch or code official that accepts it. As a A/E, we won't take on that liability without a certified letter from the manuf. saying post-manuf. process of engraving is ok.

It would be interesting to ask one of the QC test folks at your plant if they will still certify your product if it is modified in the field and if they would be willing to issue a certified letter saying it is ok to do so.

In my 42 years in the A/E field these kind of letters are easy to talk about in a meetings on the job site but are nearly impossible to get at the end of the day. I have seen less than a half dozen letters from Manuf. willing to say things are ok to do things. And anything that relates to a UL rated wall/door are nearly impossible to get.

So at the end of the day if a shop drawing came in for a tempered piece of glass that was going to be field modified by a contractor that did not come with a factory letter saying it was ok, we would reject and make him go to the code official to sign off for it, which they won't.

That is why we have specs that would say something like "modifications shall be done at the manufacturing plant prior to shipment." Some things are for example spec'd at coated before forming or coated post forming.

[Steve Utick]

I do a lot of tempered glass and generally do not agree that laser engraving degrades it. Can you cause degradation--yes, but not by engraving it using responsible settings.

I would encourage everyone that is questioning this to watch the recent episode of NOVA on PBS. They talk in great detail about the process of making Tempered Glass. A very interesting watch, and made me second guess ever doing any tempered glass. Been asked to do some in the past, but never have. Probably won't now. Episode can be watched here: https://www.pbs.org/wgbh/nova/video/beyond-the-elements-indestructible/

[Glenn Norton]

This is on a computer case so I question if it is really tempered glass (?). Customer wants to engrave logo and wording. See what he has if he ever shows up with it.

[Kev Williams]

you contradicted yourself (my opinion :) )


Engraving will not "degrade" the glass or make it less safe.....[followed by]..... Disrupting the surface compression post tempering can create a weak spot that can conceivably cause breakage.

Engraving glass with a C02 laser fractures the surface of the glass, which by definition (my opinion :) ), disrupts the surface compression...

Personally I wouldn't be afraid of engraving tempered glass where the end use would be "ornamental", or even where it would be used as simple panes, say, as dividers in a restaurant. The main benefits of tempered glass (as I understand it) is that it's brutally strong, and that IF it breaks (say in a restaurant), it becomes a zillion small, "safe" pieces of glass rather than a half dozen very sharp, heavy, dangerous swords. But just to spontaneously break- I believe ANY glass can do that. I watched the backlight in a 1975 Chrysler Cordoba implode in my work parking lot one day, for no good reason. Just KaBLOOIE and the whole inside of the car was covered with a zillion small pieces of glass ;) -- I'm almost positive it hadn't been laser engraved :D


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[Rob Luter]

It would be interesting to ask one of the QC test folks at your plant if they will still certify your product if it is modified in the field and if they would be willing to issue a certified letter saying it is ok to do so.

In my 42 years in the A/E field these kind of letters are easy to talk about in a meetings on the job site but are nearly impossible to get at the end of the day. I have seen less than a half dozen letters from Manuf. willing to say things are ok to do things. And anything that relates to a UL rated wall/door are nearly impossible to get.



I'm the guy in our company that writes those letters, and no I wouldn't write that letter. My letter would say that the glazing was produced in accordance with CPSC 16 CFR1201 Cat II, ANSI Z97.1 (Architectural) or ANSI Z26.1, FMVSS 205 (Vehicular) standards in keeping with our SGCC certifications or classification as a DOT Prime Glazing Supplier. What the purchaser chooses to do with the glazing after receipt is entirely up to them and entirely at their risk.

I guess I'd like to know what Glenn's customer has in mind. To your point, intended use and code compliance is key here. Decorative engraving on a glass jewelry box lid is one thing, and on a shower door system or glass safety railing or auto windshield is something altogether different. The last guy to modify the glass prior to installation bears the responsibility.

[Rob Luter]

you contradicted yourself (my opinion :) )



Engraving glass with a C02 laser fractures the surface of the glass, which by definition (my opinion :) ), disrupts the surface compression...

Personally I wouldn't be afraid of engraving tempered glass where the end use would be "ornamental", or even where it would be used as simple panes, say, as dividers in a restaurant. The main benefits of tempered glass (as I understand it) is that it's brutally strong, and that IF it breaks (say in a restaurant), it becomes a zillion small, "safe" pieces of glass rather than a half dozen very sharp, heavy, dangerous swords. But just to spontaneously break- I believe ANY glass can do that. I watched the backlight in a 1975 Chrysler Cordoba implode in my work parking lot one day, for no good reason. Just KaBLOOIE and the whole inside of the car was covered with a zillion small pieces of glass ;) -- I'm almost positive it hadn't been laser engraved :D

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^^ This^^

The laser melts the glass surface, but melt or fracture, it's still not recommended post tempering. All marking, etching, etc needs to take place pre tempering.


While tempering does increase the strength greatly and does improve impact resistance, the scope sections of both ANSI Z97.1 and ANSI Z26.1 both speak to fragment size being small and relatively safe. Fragmentation testing for both standards have limits on allowable fragment size by weight. The "safety" in safety glass has to do with small relatively harmless fragments. You might get scratched up a bit, but you won't get gutted like a fish.

And yes, spontaneous breakage happens although it's very rare. It's most often caused by inclusions in the glass or by thermal stress. That's one of the reasons that dark tinted glass in architectural applications is always tempered.

[Mike Null]

When I said I'd done a lot of tempered glass I meant 3 or 4 thousand pieces. I have another 500 coming this month. So far not a single break. These are cookware lids so there is some heat and some knocking around during their life.

[Rob Luter]

When I said I'd done a lot of tempered glass I meant 3 or 4 thousand pieces. I have another 500 coming this month. So far not a single break. These are cookware lids so there is some heat and some knocking around during their life.

That's much more robust than the window glass I deal with.

[Glenn Norton]

Well the customer finally showed up with the computer case glass 4 months later. I guess we will see how this works.