Lasering Glass

[Aimee Gray]

Hi Everyone

To start off with I have to say that we are new to Lasering. We purchased our first machine about a month ago. It is Xenetech 60watt. We are currently having a few problems with lasering photos onto glass. Just wondering if anyone knows of the best settings for a photo to etch onto glass. We use Corel X3.

[Joe Pelonio]

Aimee,

Welcome to the forum and the world of lasering.

The settings vary by machine but I'd suggest more speed and less power than what is recommended in your manual for glass. The way the laser works on glass chips the surface and too much power ruins the resolution
on photos, though it looks great for clipart. Buy plenty of small pieces of glass to practice on before attempting someone's momento.

If you search the forum there have been several threads on glass engraving before.

[Aimee Gray]

Joe
We have played around with our power/speed settings, from what we can see they are right. Our main problem is that the photos are coming out all white, or the face seems to come out semi okay but with the hair it doesn't come out. We are changing the photo to greyscale, playing around with the tone, then changing it to either Jarvis or Stucki then inverting it. when inverted the hair doesn't seem to out?
Aimee

[Joe Pelonio]

With clear glass you are not going to get blond hair to show up. Faces are the worst thing to do on it. I do stained glass work too, and some of the dark colored but flat smooth glasses come out nice, because they too etch white so you get better contrast. Like black marble/granite you have to invert the image. For clear, what's darker, clear or transparent white? Not much difference. Take engraved the glass in good light and move it around at various angles and you it probably looks great now and then, but you have to look close and it's not a satisfying result.

[Tom Buzz Bernard]

Great! Someone finally asked a question about lasering glass. First let me say I do not laser glass, except for an occasional favor for a friend. I do not even have spare glass in the shop to try this. I have been told get the lead out, use high water content glass, crystal will not laser well. I still cannot get a good image from one piece to the next. Out of 5 pieces of glass a friend brought over, 2 came out good the other 3 were terrible.

Recently (this week) I had a customer, 80 years wise, says he started lasering in 1992 mostly just on glass. He says the trick is to soak the glass in warm water for at least an hour, dry it off, then laser it. He says it will come out perfect even on crystal. He told me the glass will soak up some water and make it laser. He also does sand blasting and prefers the look of lasering on glass using this method. Now this alone surprised me and made it sound plausible?

Now I haven't tried contacting MythBusters yet But he sounded very convincing. Does anyone have some glass to try this out and let us know if it works. Something so simple, could this be the magical cure for lasering glass? Is there a Mythbuster out there willing to try this

[Rodne Gold]

Pure glass wont laser , the way it works is that when the beam hits the normal type glass the impurities expand at a different rate to the glass itself with the thermal shock of the beam and this promotes promotes a shattering rather the controlled chip of blasting.
As a matter of interest , glass is not a solid , its a supercooled liquid.

Best strategys are the damp newspaper or toilet paper over the lasered area which will tend to localise the heating , Failing that , use dishwashing liquid brushed on the glass and let it dry , this tends to "damp" the glass and reduce uncontroiled shattering , masking tape does more or less the same but leaves a residue.
Lower resolution works better on glass than high , having laser pulses overlapping a lot will only increase the chance of a more "shattered effect and loss of detial.

I have no idea about the warm water thing , barring the fact that glass is NOT porous and wont retain any water so that premise is false which kinda once again blows that one out the water

As to lasering being better than sandblasting , well it is and it isnt. Solid area type sandblasting will blast the same thing done using a laser out the water as you can never get the smoothness and depth of sandblasting. Very fine detial cannot be blasted properly , especially photos (there is a method of using a laser to make a mask , but the mask has to have big enough openings for the grit to penetate and this makes for poor and dotty resolution with pics) and here *any* lasered output will be "better" than sandblasting.
The laser will certainly outperform traditional blasting techniques especially with respect to doing detailed stuff on compound curves which is almost impossible using decorative sandcarving and can be done real quick and easy with a laser.

Rubbing the engraving with a scotchpad after often helps with the "glass splintery" type feel and rubbing it with silver or white wax paste like Rub-n-buff and buffing the residue off helps whiten it up a LOT

In general front engraving using a laser gives better results than reverse , for blasting , reverse always almost works better , especially with mirrors. The results here have much more "depth" to them.
Other options are to spray paint the back of the glass black and then laser in reverse (inverting the pic so white is now black) , this you can spray white or just leave lasered for pretty good results.
We use an anodised aluminium sheet under glass when lasering as anodised ally acts as a beam stop and wont let the beam reflect around (we raise the glass so its about an inch or 2 above this sheet and we like to use black anodised , we use this under just about everything)
Hopes this helps a little.
Regards Rodney

[Mike Mackenzie]

The only way we have ever been able to get a decent photograph on glass was to use photograve. Glass is a material that will not give you 16 shades of gray.

In My opionin it must be photo graved before the process then it is hit and miss.

Here is an example of one that was done with photograve

[Jesse Anderson]

Glass does in fact have water in it i think.. Referencing a article i read on the internet... Because glass is a “natural” material (that is, its primary elements come from nature), one would think a CO2 laser would engrave glass pretty well. Ironically, it really does not engrave glass at all but it will mark it and with that contradiction, we will begin to understand how a CO2 laser beam interacts with glass.
In the most basic of terms, glass is made by heating silicon (sand). When heated hot enough, the silicon melts and becomes a thick, gooey fluid. This can then be poured into molds or blown by hand. As the molten glass cools, it remains transparent. To add strength or color to the glass, other elements are added. These are often metals such as lead, zinc, cobalt or even pure gold. In the case of lead, a considerable amount can be added to glass without affecting the transparency of the glass as you can see in 24% leaded crystal. 24 Karat gold on the other hand, produces a unique colored glass called cranberry.
Understanding this part of the process is important to laser users because, as all experienced laser users know, you cannot mark metal with a CO2 laser and that is just as true when the metal is molten (in glass) as it is when metal is in a sheet form.
So, thus far, we have learned that CO2 lasers can’t engrave glass, nor can they deal with the metal content of glass, yet we have all seen glass items marked by lasers. What gives?
This is really not as much a paradox as it might appear. Remember how glass is made? Silicon is heated to 2000 deg or more until it becomes molten. It is then removed from its oven and manipulated in some way. This introduces two things into the glass beyond its basic elements: air and moisture.
It’s the air and moisture that’s trapped within the glass that makes laser marking possible with a CO2 laser.
As a laser beam strikes the glass, it heats up the glass elements including the silicon and any metal content but neither of these elements will react to the relatively low heat and frequency of a CO2 laser. What does react is the air and moisture trapped between the elements of silica and metal. Both water and air expand when heated. Because the glass itself is relatively rigid, when molecules within the glass are heated until they expand, something has to give to allow for the expansion. This results in microscopic fractures in the glass, especially at the surface of the glass. It is this chipping or fracturing that we see as engraving.

[Kev Williams]

As Mike mentioned, there are no gray shades when engraving glass, it's totally binary. It's either engraved, or it's not. Ergo, the only way to satisfactorily engrave a photo in glass is in halftone. I've never seen photograv (or any other laser photo software for that matter) so I have no idea if I could make it work or not. The only halftone 'generators'(?) I've used is what's in Corel, and the actual "halftone" choice is a complete joke. And while the Floyd's & Stucki's work so-so on materials with good contrast, they're terrible on glass. Seems to me that a pure round-dot halftone, exactly like newspapers have always used to print black/white photos, would be the best way to reproduce photo's on glass, and even then you're at the mercy of the smallest dot your laser will make, which isn't all that small.

I have a couple dozen elcheapo mirror tiles in the back room, every so often I'll drag one out and make another attempt at lasering a photo. In all the years I've had these lasers, I've yet to get a satisfactory result. Maybe with a decent halftone program I could. Fortunately, I don't get many request for glass photos.

[Kevin Gregerson]

I'm happy to test most of your glass samples for you. My little 50 watt has done an outstanding job on every glass job I've done with it.

[Grant Lomman]

I tried leaving a glass in both warm water and in the freezer and neither temp changed the quality of glassware engraving. I find the glass itself is usually the most determining factor.

[Jed Lawrie]

I tried leaving a glass in both warm water and in the freezer and neither temp changed the quality of glassware engraving. I find the glass itself is usually the most determining factor.

^This^. I find that the cheaper the glass, the better it engraves. That my have to do with the fact that the cheap glass is not as pure as the expensive stuff. I am not an expert on the subject. There are some guys on here that swear sand blasting is the only way to work with glass. I've never sandblasted before though.

[Brent Franker]

I found this video on YouTube to be informative and impressive. I have not yet tried it myself but I'm very much impressed with the end result.

https://www.youtube.com/watch?v=dvV_E82ztk0&list=WL

[Dan Hintz]

Glass does in fact have water in it i think.. Referencing a article i read on the internet... Because glass is a “natural” material (that is, its primary elements come from nature), one would think a CO2 laser would engrave glass pretty well. Ironically, it really does not engrave glass at all but it will mark it and with that contradiction, we will begin to understand how a CO2 laser beam interacts with glass.
In the most basic of terms, glass is made by heating silicon (sand). When heated hot enough, the silicon melts and becomes a thick, gooey fluid. This can then be poured into molds or blown by hand. As the molten glass cools, it remains transparent. To add strength or color to the glass, other elements are added. These are often metals such as lead, zinc, cobalt or even pure gold. In the case of lead, a considerable amount can be added to glass without affecting the transparency of the glass as you can see in 24% leaded crystal. 24 Karat gold on the other hand, produces a unique colored glass called cranberry.
Understanding this part of the process is important to laser users because, as all experienced laser users know, you cannot mark metal with a CO2 laser and that is just as true when the metal is molten (in glass) as it is when metal is in a sheet form.
So, thus far, we have learned that CO2 lasers can’t engrave glass, nor can they deal with the metal content of glass, yet we have all seen glass items marked by lasers. What gives?
This is really not as much a paradox as it might appear. Remember how glass is made? Silicon is heated to 2000 deg or more until it becomes molten. It is then removed from its oven and manipulated in some way. This introduces two things into the glass beyond its basic elements: air and moisture.
It’s the air and moisture that’s trapped within the glass that makes laser marking possible with a CO2 laser.
As a laser beam strikes the glass, it heats up the glass elements including the silicon and any metal content but neither of these elements will react to the relatively low heat and frequency of a CO2 laser. What does react is the air and moisture trapped between the elements of silica and metal. Both water and air expand when heated. Because the glass itself is relatively rigid, when molecules within the glass are heated until they expand, something has to give to allow for the expansion. This results in microscopic fractures in the glass, especially at the surface of the glass. It is this chipping or fracturing that we see as engraving.

This is a load of bunk, plain and simple. You simply will not have moisture of any kind trapped inside an object that was recently 2000 degrees. Common sense should tell you that if water boils at 100 Celsius, a thin skin of water will flash away in a millisecond... not to mention you'd create an explosion if you introduced water into a mold at 2000 degrees.

This is an old thread, but I have since posted on several occasions as to the true cause of engraving glass. It is caused by the localized stresses created during cooling, not heating (and therefore has zero to do with impurities, oxygen, water content, etc.). A CO2-wavelength laser can only penetrate glass a few tens of micrometers, which makes it a good shield for our purposes.

[Bill Cunningham]

I posted a file a while back, an a sample of what it will engrave (magnified housefly, with lots of detail)like. This is a well tested file so run it at several settings using 300 or 600 dpi and find out the best setting for 'your' machine. I can't repost it from my tablet, but a search will turn it up