View Full Version : Laser Glass

Larry Crim
09-16-2004, 12:12 PM
I am building a display case that will require some laser etching on the glass, My question is how thick chould the glass be I have heard that it needs to be a minimum of 1/8 th inch to be laser etched is this true?

George M. Perzel
09-16-2004, 12:44 PM
Hi Larry;
Never heard that before. I have laser etched glass thinner than 1/16" and not had any problems. What is supposed to happen if it's not a minimum of 1/8"?

Larry Crim
09-16-2004, 1:55 PM
Not sure
Its something that someone had told me in the past, He said that he was getting some laser engraving done and the vendor told him he would not gaurentee the work it the glass was less than 1/8th", so just thought I would ask to be safe.

Kevin Huffman
09-16-2004, 3:02 PM
Hey George,
The reason the vendor probably didn't want to do the job is becuase of breakage. If the power/speed isn't right for that glass, you could easly shatter it. Glass is senstive to heat. But there is no limit to how thick or thin your glass can be, as far as our lasers are concerned.
He was probably worried about having to clean up the glass if it did shatter.

George M. Perzel
09-16-2004, 6:18 PM
Hi kevin;
You are probably right-guy didn't want to take the chance. I have done some thin crystal which worked great-didn't know enough to be concerned. I guess the guy upstairs protects the dumb and ignorant.
Now you guys got me thinking and I'm going to try to destroy some different thicknesses of glass and see what the limits are. Will post the results.

Michael Wells
09-16-2004, 10:10 PM
Okay guys, stay with me here...I know this is going to sound goofy, but it's true stuff!

Glass is a liquid, (honest!) albeit a very highly viscuous one, and therefore when extreme heat is applied it converts to the next highest form, a gas. Usually a material that converts rapidly to gas expands rapidly and this is what causes the glass to shatter. Now for the good news, the photons of a laser light go right through a clear viscuous liquid without causing much heat in most cases. That is why you need to cover the glass with paper (or something)...to cause the heat to etch the glass and also why the lenses of the laser do not etch when it is fired.

Now, the best glass to use is one that contains a high level of lead in it for laser engraving, which is usually the cheapest glass you can get or the most expensive of crystal, and the lead causes some internal heating when the photons pass through the glass. Unless you are using YAG, if you use a very high lead content glass and very thin also, you might shatter it if you expand the gasses to rapidly, but I would think that you would have to really power up and slow down to heat it enough to cause a problem. Even at that, the paper covering holds most of the heat and if it is wet down first, generally speaking, unless you were to have a seriously high power rig, I don't think you would shatter the glass very easily. It could be done, but I think you would have to really be trying to get it hot!

Okay, now all of you can tell me to go back to the lab, Igor...we don't really care! Hehehe

Keith Outten
09-16-2004, 10:27 PM
Thanks Mike,

I'm always interested in the details...the more you understand the better decisions you can make concerning materials. I have engraved lots of glass but I don't recall ever using glass thinner than 1/16". I often engrave glass without any paper, it is a matter of quality and price. The highest price glass engraving I do involves using wet newspaper but it takes more time and if the job is long I have to stop frequently to re-wet the paper. Also there is more risk using wet paper, if it drys during the job run it will separate from the glass and the project is history, that is why I charge more for higher quality glass work. The good news is that the quality of engraving with wet paper is just awesome, the best I have ever seen.

Glenn Palhof
03-26-2005, 11:06 PM
I find the etching with the paper most interesting. what differences will i see? Is there a particular type of laser that you use newspaper. My machine is completely open as it is for monument work. I have been doing it without paper.
thanks glenn palhof

Rodne Gold
03-27-2005, 12:18 AM
The glass does not vaporise with the type of lasers we use , its impurities just heat, expand and shatter the glass locally. This fracture is uncontrolled to a large extent , and that combined with the uneven distribution of the impurities are the cause of the lousy or variable engraving quality when lasering various glasses.
The wet paper is merely a heat sink and a "damper" All it does is localise the "heat hit" and minimizes the effect on adjacent areas much like soldering using paste that stops other areas getting heated. The damping effect is related to this but is mechanical , what happens is the same as engraving/cutting glass under water , the fracture cannot progress to a crack as the wet paper effectively dampens the shock wave , ie doesnt allow the fracture force to propgate thru the rigid glass. Easily demonstrated by tapping the glass with and without the wet paper , without the glass will "ring" , with the tap will sound dull and thus demonstrate that the wet paper is indeed damping mechanically too.
You can add glycerine , diswashing liquid or any other agent that will retain the moisture or prolong the wetness of the paper to stop it drying. We actually get better effects with wet paper based vinyl transfer tape as the paper tends to retain moisture better , wont come adrift and the adhesives dampen mechanically even better than wet paper.
We turn air assist off when lasering glass - it stops excessive drying if wetted and the blowing off of the dry paper if we do use toilet tissue or newspaper , but more importantly it lessens the distribution of the glass dust lasering produces if you are not doing "wet" lasering.
We often are asked to laser 2mm glass or thinner with no problems at all.
For those that blast , here's an interesting application , wherever you lasered glass will blast deeper than the surrounding glass. You can get a very subtle 3d effect on blasted glass if you lets say engrave a pattern on it and then blast the whole piece. The lasered areas will not be obliterated but will just go deeper. Very much like a 3d sandcarved effect.

Glenn Palhof
03-27-2005, 9:26 PM
I have transfer tape to try. We did a couple of wedding glasses friday.We lasered the vinyl resist. applyed to glasses with transfer tape then blasted with a superfine grit. We have done some directly from the laser. some glass are so curved the etch can become distorted. We are in the process of designing a simple type of a craddle to follow the laser and rotate at the same time.This week we will engrave glass with the wet system. I enjoy reading the articles you have been writting. I have been learning so much from you and all the other members.If you would like to see some of our works, go to my log in name "Glenn Palhof" and clik on my name.I have started a library file as a resource center to help with problems we encounter.WE spent 8months just doing R&D making a chart of different materials.We use it all the time due to alzheimers.

thanks Glenn