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Scott Moore2
07-16-2012, 7:01 PM
Hi

We just had someone come in and ask us to engrave on glass pipes. They want us to do them regularly, all the same logo on every one, and it looks like a couple hundred a month. Seems a pretty nice commercial job.

Here's the catch. It's pyrex. So we tested on glass, and it the logo comes out fine. We fine tuned for our laser, and found the magic formula. Then we tried on their glass pipe. No go. It chips rather than really etching. If we turn down the power a lot, we sort of get an etch, but it's not really clear. Turn up the power and the glass chips away.

This makes sense to me technically. The pyrex doesn't want to be engraved by heat, as it's heat resistant. But I thought I'd ask you kind folks here on the forum before I give it up.

scott

matthew knott
07-16-2012, 7:07 PM
does the logo start with PAS? out of interest !

Ross Moshinsky
07-16-2012, 7:55 PM
Sandblasting is going to give you perfect results every time.

AL Ursich
07-16-2012, 9:16 PM
I had seen some use a wet newspaper on the Pyrex too.... ( My Laser Friend Lisa that gave up her Laser about 4 years ago. )

Sand Blasting sounds like a better deal.... Even Laser the Blast Film attached at low power then Sand Blast would be a option.

Just know that Glass is a Liquid that is solid at Room Temperature. From the Sony CRT Glass class... (1995). I would lean toward more Sand Blasting as the Heat could cause Micro Fractures that could show up later as a failure.... At Pressure.... This is due to the Stresses built up in the Glass during Laser Engraving... Sony and many Glass Processes use a Post Annealing Process to reduce the stress.

http://en.wikipedia.org/wiki/Annealing_(glass)

I am really going off the DEEP END but just Food for Thought.... A call to the Glass Manufacturer Engineering Dept might put your mind at ease. A Release of Liability might be good too....

Good Luck,

AL

Mike Null
07-16-2012, 10:27 PM
Pyrex is not any more heat resistant than other glass, they are after all, made for baking. Experiment with your settings more. You should be able to do it.

Sandblasting will produce a good image but may be too expensive for the job.

Rodne Gold
07-17-2012, 1:54 AM
Try engrave it using a vector mode rather than raster , pyrex doesn't do the heat fracture chip thing well , but it will actually "engrave" , you wont get a "sandblasted" mark , more like a clear groove....
Check out Synrads markings on pyrex.
http://www.synrad.com/search_apps/application_briefs/9-5.htm

Braden Todd
07-17-2012, 9:54 AM
Are you sure that they are using Pyrex for their pieces? The guys around me use borosilicate glass (I forget the exact Coe right now), I have had the same issues as what you are experiencing but only with certain colors. As many others have mentioned, sandblasting is a great way to go with this project if their budget allows.

I have had really good luck with clear boro and the laser though.

Good luck!

Steve Clarkson
07-17-2012, 11:08 AM
Cermark on Pyrex works very well.

Richard Rumancik
07-17-2012, 11:27 AM
I don't think you can use Pyrex and borosilicate glass as interchangable terms. Pyrex bakeware used to be a Corning product and originally was borosilicate. But along the way Pyrex became more of a trademark rather than a brand-name signifying borosilicate glass exclusively. Corning doesn't make the bakeware line anymore (they have sold a license) and I don't believe any of the current bakeware is borosilicate glass.

The main feature of borosilicate glass is it's resistance to breakage when subjected to uneven cooling (eg one corner of a hot piece of glassware subjected to rapid cooling. Most glass will shatter when this happens due to high local stress.) Some people call this "heat resistance" but it is not the heat that shatters glass, it is uneven expansion and contraction. Borosilicate glass is resistant to breakage from rapid temperature changes, not just to the temperature itself.

On the website for the current manufacturer of Pyrex-brand bakeware they say not to place hot bakeware on a damp towel. If it was made of true borosilicate glass, it could withstand this without a problem.

I think Corning still makes laboratory and industrial borosilicate glass under the Pyrex brand. So chances are industrial products will not be soda lime glass, but you have to ask if it is borosilicate glass.

But if people have done laser tests on bakeware, you can't assume that the results are applicable to borosilicate glass.

Scott, I expect that your glass "pipes" are really borosilicate. The reason normal soda line glass will laser-etch is because the laser induces high local temperature changes that cause it to fracture and a small piece flakes off. The borosilicate glass by definition is more tolerant to the local temperature change, and so it will not flake off quite like soda lime glass.

Ron Natalie
07-17-2012, 12:25 PM
Richard is right. PYREX was originally Corning's trademark for borosilicate glass. To confuse the matters both Corning and another company (under license for the trademark) make stuff under the Pyrex name which in some cases is borosilicate and in others soda lime glass. Corning by the way didn't invent it, Schott (the German equivalent of Corning) did two decades before Corning started producing it.

The Corning museum has a neat T-Shirt in their gift shop showing a person "Stressed" and "Annealed."

Scott Moore2
07-17-2012, 6:48 PM
Thank you all. Richard that was very helpful.

I suspect that Richard is right, and these things really are borosilicate. In any event, after reading everything here and trying a few more settings, I've determined this is not a job I want. I'm going to recommend that he find someplace that does sandblasting.

This has also opened my eyes to new possibilities with sandblasting for my business, and may buy what I need to offer sandblasted engraving and add that to my business.

thanks again everyone. Very helpful indeed.

dave cox
07-17-2012, 9:36 PM
Try wet paper towel or similar, also dish washing liquid can work well, it tends to keep chipping down and usually will give a finer finish which looks more like sandb lasting.

matthew knott
07-18-2012, 3:18 PM
We engrave lots of Pyrex tubes, (500 a week) with a simple logo. The machine we use does a rubbish job on glass but seems to engrave these just fine. It has a long focal length lens (150mm) and we use it in vector mode at a fairly high speed. Its the one glass job we can get to work on it, maybe put your laser out of focus and run it, might help