Masking / Coating Glass before Engraving

[Jack Clague]

Hi All,

Most if not all the videos and documents I have read on glass engraving states to either cover in a wet newspaper for frost effect or masking tape for a smooth etched effect, this i presume is also to help stop chipping of the glass?

Any particular masking tape that is used? having a hard time finding wide rolls of masking tape in AU

Jack

[Kev Williams]

Wives tale. Nothing you cover the glass with that the laser will burn thru will make one bit of difference to what it does to the glass...

It's like the tall tale that your tires will protect you if a 6 mile long/1000 gigawatt/30,000 amp lightning bolt hits your car. Nope. 3" of rubber ain't gonna help! (although the metal does... :) )

-- same goes for that laser beam. Some tape or a wet paper towel isn't going to affect that beam in the least as it hits glass.

A year ago I had a wine bar restaurant wanting me to laser etch their logo into wine glasses. I tried every trick I could think or read about, spent days experimenting. Results never changed. The only thing that actually does help is to lower the black level of your text or image and let the laser run a ditherered output. The random spacing of the output prevents multi-overlapping of the beam path, which helps quite a bit with the fracturing problem...

[Jack Clague]

Wives tale. Nothing you cover the glass with that the laser will burn thru will make one bit of difference to what it does to the glass...

It's like the tall tale that your tires will protect you if a 6 mile long/1000 gigawatt/30,000 amp lightning bolt hits your car. Nope. 3" of rubber ain't gonna help! (although the metal does... :) )

-- same goes for that laser beam. Some tape or a wet paper towel isn't going to affect that beam in the least as it hits glass.

A year ago I had a wine bar restaurant wanting me to laser etch their logo into wine glasses. I tried every trick I could think or read about, spent days experimenting. Results never changed. The only thing that actually does help is to lower the black level of your text or image and let the laser run a ditherered output. The random spacing of the output prevents multi-overlapping of the beam path, which helps quite a bit with the fracturing problem...

Its gotten pretty wide spread for a wives tale, big companies such as Trotec show these methods in their videos (Trotec Canada Etc)

I might have to run some tests up and see if there is any difference.

[Kev Williams]

My NH rep showed me the wet paper towel trick years ago. It's a "factory" thing I guess...

If the wet paper is somehow supposed to alter the beam by cooling it or refracting it, I really don't see how a damp piece of .008" thick paper is going to change much of the 5000-10000 watts of light energy hitting it before it hit's the glass? Seems easier to achieve the same/better results by power and focus adjustments...

[Tim Elmore]

You're using a 10kw laser to engrave glass?

The wet paper towel won't do much for the beam, but it will hold down temperatures in the surrounding glass, reducing thermal stresses.

[Neal Schlee]

I use blank newsprint and a spray bottle with water, making sure you don't have any air bubbles when lasering.
Been doing it this way for 20 years and thousands of glasses, while not completely eliminating the chipping it definitely helps to minimize it.

Just do a side by side comparison.


Neal

[Keith Winter]

You are correct Tim, the wet paper helps displace the heat which helps control the fracture. Disadvantage is the paper can dry out while running enough to get lifted up a tiny the exhaust, which will create a bubble as Neal said ruining your engraving. So make sure it's fairly wet. Any way you do glass you will have mistakes and waste, glass is notorious for engraving inconsistently, so be prepared for that. Only way to 100% eliminate mistakes is to use the laser to cut masks then sandblast. However that opens up it's own set of issues and is fairly messy. Anyway you look at it glass is a bear ;).

[Jack Clague]

Thanks for the comments guys, good to hear, I will be sure to iterate to clients how fragile glass can be when quoting a job, I've got a client wanting 40 Candle Jars engraved so will build in some buffer to cover any ones that do not come out ok.

[Jeffrey Dewing]

I have a speedy 300, 80 watt, and run the glass at 65 P. and 100 S. depending on the type glass and it comes out well. You can then wash it, an rub on Rub'n'buff paint for different effects. I've never had much luck with soapy news paper...

[Jack Clague]

Hi Guys, I thought I would share my experiments today.

Below are 3 sets of pictures in different lighting and orientations of exactly the same images engraved at the same time with the same focus and settings

Glass was scrubbed and cleaned after engraving was done



The images on the left were engraved without any form of paper or masking, glass was cleaned before hand




The images on the right were engraved using a low grade copy paper soaked in natural window cleaner, applied to the glass and smoothed for bubbles


Image with black liquid inside glass:
323961323962

Image with a slight top down view on kitchen bench background
323963323964

Image with straight on view and brownish background
323965323966

My assessment from today's testing

The wet paper is doing something, my limited experience is telling me it is helping keep the image sharp and "frosty" by keeping all the micro shards of glass that will flake off when the laser hits from being remolded back to the glass while the laser passes over the surface or while the surface is still hot

The feel of each is only slightly different with the "wet paper" version being slightly smoother to touch

Next time i get some time to test I will try another glass, same image but this time add in masking tape to see if there is any difference between masking tape and wet paper.

[Scott Shepherd]

Jack, if you are up for testing, smear a film of dishwashing soap on one and try that.

I don't know what to believe with glass. People I have a lot of respect for say it absolutely makes no difference, while others that I respect just as much say it makes all the difference. In my experience, glass varies a HUGE amount, even from glass to glass. In my experience with glass, you could get one glass perfect and they next one would be chipped out on the edges, with the exact same settings and method. Engraving glass on the laser was a completely unpredictable experience. Wait until you do some plate glass and one letter of of a word doesn't show up at all. I've talked about it before, but when engraving plate like that, you can some times stare at the engraving, after it's engraved, and you'll see a letter or letters completely missing and like magic, before your eyes, they will instantly appear. I guess the glass cools enough that it finally breaks on the micro level, and the entire letter appears. It really does look like magic.

For me, that just didn't work, which is why we bought a sandblasting cabinet. Now, we don't fight with glass any more :)

[Keith Winter]

Those look good jack. I cannot really tell the difference in the two photos, based on what you said I guess there is a noticeable difference in person on left vs right?

In the interests of curious minds, try something for us. Engraving them correctly is a tough skill to master and repeat, getting them to stay that way is even harder. I don't know how many times I've walked up to Epilog/Universal's booth rubbed my thumb across their glass and shards flaked off onto my thumb. Try running them in the dishwasher on the HOT setting. Curious to see if you start to get some areas of the white that flake off after 3 runs, and if one engraving method stays better than the other?



Hi Guys, I thought I would share my experiments today.

Below are 3 sets of pictures in different lighting and orientations of exactly the same images engraved at the same time with the same focus and settings

Glass was scrubbed and cleaned after engraving was done



The images on the left were engraved without any form of paper or masking, glass was cleaned before hand




The images on the right were engraved using a low grade copy paper soaked in natural window cleaner, applied to the glass and smoothed for bubbles


Image with black liquid inside glass:
323961323962

Image with a slight top down view on kitchen bench background
323963323964

Image with straight on view and brownish background
323965323966

My assessment from today's testing

The wet paper is doing something, my limited experience is telling me it is helping keep the image sharp and "frosty" by keeping all the micro shards of glass that will flake off when the laser hits from being remolded back to the glass while the laser passes over the surface or while the surface is still hot

The feel of each is only slightly different with the "wet paper" version being slightly smoother to touch

Next time i get some time to test I will try another glass, same image but this time add in masking tape to see if there is any difference between masking tape and wet paper.

[Ron Sleeman]

Jack, did you change your settings to the one I did. They look great

[Ross Moshinsky]

Wives tale. Nothing you cover the glass with that the laser will burn thru will make one bit of difference to what it does to the glass...

It's like the tall tale that your tires will protect you if a 6 mile long/1000 gigawatt/30,000 amp lightning bolt hits your car. Nope. 3" of rubber ain't gonna help! (although the metal does... :) )

-- same goes for that laser beam. Some tape or a wet paper towel isn't going to affect that beam in the least as it hits glass.

A year ago I had a wine bar restaurant wanting me to laser etch their logo into wine glasses. I tried every trick I could think or read about, spent days experimenting. Results never changed. The only thing that actually does help is to lower the black level of your text or image and let the laser run a ditherered output. The random spacing of the output prevents multi-overlapping of the beam path, which helps quite a bit with the fracturing problem...

It's absolutely not a wives tale. The wet "paper" cools the glass and takes some of the blow out of the laser beam hitting the glass.

As I've said previously, I don't get shards of glass after engraving. I don't dither. I don't do anything. I run at 30W, 500DPI, slowish speed, and use wet packing paper. My results look similar, but not quite as good, as if you just quickly sandblasted without getting any depth. The only thing else I can say about glass/crystal is make sure your material is in focus.

[Kev Williams]

Everyone's laser is different. Here's what I found in my testing-- One test doesn't work. Four or five tests don't work. Twenty tests, maybe...

Every time I thought I'd hit on something, a couple of parts later proved me wrong.

and btw, I've never got glass shards, regardless of paper or not. What I DO get is banding, just like Jack got. (And my ULS has NEVER left banding on anything. Again, all lasers all different)

Just my experiences...

For another test: Change that tiger to 70% black and run it in photo mode at 75% power and 40% speed. You should see less pitting and way less banding...

[Jack Clague]

Thanks guys,

This is an awesome discussion for me as I love working with glass, I don't want this to turn into a row over if it works or not, frankly as Kev said everyone's setup will be different, I'm guessing the ambient temperature of the room and temperature of the glass will also play a big effect on glass engraving , from my tests so far the wet paper is doing something for my setup, so I'm happy to keep testing to see what I can ascertain

Previous settings used were 100% power, 50% speed, 500DPI, Jarvis

So for my next few tests I will be doing:



Multiple hot dishwasher cycles on the worked pieces to see which ones change if at all
70% black engraving at 75% power 40% speed, same DPI and Differing Protocol (Not sure what you mean Kev when you say "Photo" Mode)
Engraving on Hot and Cold glass, to check if there is any effect from a glass that is at a high temperature (hot day) or low temperature (cold day)


Steve I tried the film of liquid but it dried way too quickly, I think they talk about using paper so it retains the liquid long enough to get the engraving done

Ron, same settings as your glasses apart from the Eagle, that was a higher speed 60% i think

[Jack Clague]

Here is the Eagle I did as well, eagle was done with wet paper, text was not
324009

[Dan Hintz]

Hi Guys, I thought I would share my experiments today.

Below are 3 sets of pictures in different lighting and orientations of exactly the same images engraved at the same time with the same focus and settings

Glass was scrubbed and cleaned after engraving was done



The images on the left were engraved without any form of paper or masking, glass was cleaned before hand




The images on the right were engraved using a low grade copy paper soaked in natural window cleaner, applied to the glass and smoothed for bubbles



The wet paper is doing something, my limited experience is telling me it is helping keep the image sharp and "frosty" by keeping all the micro shards of glass that will flake off when the laser hits from being remolded back to the glass while the laser passes over the surface or while the surface is still hot

The feel of each is only slightly different with the "wet paper" version being slightly smoother to touch

Next time i get some time to test I will try another glass, same image but this time add in masking tape to see if there is any difference between masking tape and wet paper.

Did you change the settings between each test? If not, it's not a valid test. The glasses on the left look like too much power, hence the chipping. Too much power will also remove the fine detail.

The dwell time of the beam at each location as well as the power density and size of the focal point simply does not allow for "local" cooling by water (not to mention H20 is a great blocker at the CO2 lase wavelengths). High heat is needed to melt the glass, because it's the cooling of the glass that causes the fracture (which is what provides the frosted effect). By attempting to cool the glass, you're merely requiring more heat to cause the fracture.

[Jack Clague]

Did you change the settings between each test? If not, it's not a valid test. The glasses on the left look like too much power, hence the chipping. Too much power will also remove the fine detail.

The dwell time of the beam at each location as well as the power density and size of the focal point simply does not allow for "local" cooling by water (not to mention H20 is a great blocker at the CO2 lase wavelengths). High heat is needed to melt the glass, because it's the cooling of the glass that causes the fracture (which is what provides the frosted effect). By attempting to cool the glass, you're merely requiring more heat to cause the fracture.

Thanks Dan, It was identical settings the only difference is the masking used, so your saying that the images on the left would be close to if not identical to the right If I adjusted the power, as the images on the right were done with a wet paper mask the H2o is effectively blocking the CO2 wavelength and reducing its power into the glass?

So reducing the power may yield the same results as the "wet paper" method, will continue to test :)

[Dan Hintz]

Thanks Dan, It was identical settings the only difference is the masking used, so your saying that the images on the left would be close to if not identical to the right If I adjusted the power, as the images on the right were done with a wet paper mask the H2o is effectively blocking the CO2 wavelength and reducing its power into the glass?

So reducing the power may yield the same results as the "wet paper" method, will continue to test :)

Glass is somewhat finicky... certainly more finicky than, say, anodized aluminum (one of my favorite substrates). But don't take that to mean it's not possible to get a consistent engraving. As I've mentioned many times over the years, the main mode of engraving glass is based upon fractures during cooling of a locally melted spot. Too much fracturing in one area leads to chipout. To avoid chipout, the fractures should be controlled, either in size (the more difficult option) or in closeness to each other (much easier to control).



FULL DISCLOSURE: I have received PMs in the past asking my take on water, coatings, etc. There is an effect seen with any/all of the above, and I have done many experiments myself over the years (both for my business and work... it's nice when someone pays you to play), but it is not as direct as the majority here believe and requires some VERY controlled environmental variables to have a proper effect. Because of that, I always suggest against people spending time trying to recreate those circumstances. When I post my workshop is back up and running, I will count on one of my fellow laser buddies here to remind me of the following... to run some more tests and show the results from under the microscope to more fully detail what happens when you try to control the fracturing process.

[Jack Clague]

Glass is somewhat finicky... certainly more finicky than, say, anodized aluminum (one of my favorite substrates). But don't take that to mean it's not possible to get a consistent engraving. As I've mentioned many times over the years, the main mode of engraving glass is based upon fractures during cooling of a locally melted spot. Too much fracturing in one area leads to chipout. To avoid chipout, the fractures should be controlled, either in size (the more difficult option) or in closeness to each other (much easier to control).



FULL DISCLOSURE: I have received PMs in the past asking my take on water, coatings, etc. There is an effect seen with any/all of the above, and I have done many experiments myself over the years (both for my business and work... it's nice when someone pays you to play), but it is not as direct as the majority here believe and requires some VERY controlled environmental variables to have a proper effect. Because of that, I always suggest against people spending time trying to recreate those circumstances. When I post my workshop is back up and running, I will count on one of my fellow laser buddies here to remind me of the following... to run some more tests and show the results from under the microscope to more fully detail what happens when you try to control the fracturing process.

Thanks Dan,

I think I will just find a setting I am happy with and work with that, like you said the material is finicky and I understand the thermal fracturing of the glass will be different based on allot of outside factors, so my settings in summer here in AU may be different to winter, same with the effect of any cooling masks

[Kev Williams]

I will concede that "wives tale" may be a stretch.. -- Because, I ran a few tests, and yes, I found a difference when using an 'additive'. During my tests, in which I used wet newsprint, the main difference I found was that I had to slow the machine down in order to get a decent burn. And once I got a decent burn, yes it was different than the test without wet paper. So while I have to say there was a difference, I stand by this assertion: whatever happens because of tape, wet paper, soap, etc. can likely be reproduced with a few power, speed and resolution tweaks.

Below are a few pics. I ran the same logo I do for my wine bar customer on an old sample glass.
The first 2 test were run at 100 power (40w), 50% speed, 500 dpi X&Y. Here's the first,
no paper. Notice the banding is pretty bad towards the top, and from there down is a lot of 'rippling'...

324096324095


Next I wet a piece of newspaper, and found it killed the power, so I went from 50 speed to 30.
The banding is almost gone, but not the rippling. And quite a bit of fracturing. Probably because of TOO slow...

324097
So I ran another paper test, at 35 speed. Only ran half the logo... The first pic looks pretty good, except for some blotchy under the "G"
The second pic with a little different light shows light rippling and a little banding..

324098324103

Finally, my dithered test, below. 70% black, ran at 100 power 50 speed, but only 300 dpi both directions...
There is a bit of fracturing along the right-top of the bottle neck.
That can probably be helped out by going faster and/or less power, and upping the DPI to 400 or 500,
although I've found more than 400 dpi gets the dots so close it can defeat the purpose.
But as you can see, there is little or no rippling, and no banding. The dithering has created a nice,
bandless, blotchless consistent etch with some minor issues that can likely be helped with a few tweaks :)

324102324101


=================
As for "what is photo mode?" -- My LS900 driver has a typical grayscale mode, with a dark-to-light adjustment slider,
and it also has a set-it-and-forget-it photo mode, adjustments are power, speed and DPI like with solid colors.
It seems to result in a more consistent pattern than the grayscale. However, my ULS's plain old halftone settings
give me great results. (just can't do glasses!)

[Dan Hintz]

So while I have to say there was a difference, I stand by this assertion: whatever happens because of tape, wet paper, soap, etc. can likely be reproduced with a few power, speed and resolution tweaks.

This is my assessment, as well (except I would remove the word "likely").

[Ron Sleeman]

I like to add one other factor, is the angle the Rotary attachment.I find that the angle that you put your glass in is very important. Check out the place's where the the heat hits hard to the other areas the heat hits less, you will see the differents. Plus, I never use soap or paper on my Epilog or now my new speedy 400 80 watt...lol. Plus we just did 300 Glasses for one of our companys and if I had to put paper or soap on each one, I would loose money..lol....time is important.

Thanks Ron Sleeman

[Keith Winter]

Try running it in the dishwasher. Curious what it looks like after 3 washes on hot, if it starts to flake off?

[Chris Achtschin]

Funny how this thread comes up while I'm lasering glass paper weights.
I'm wetting down packing paper and lasering twice for a decent result.
If I use no paper I get a lot of missed etches and chipping.

[Kev Williams]

Try running it in the dishwasher. Curious what it looks like after 3 washes on hot, if it starts to flake off?

Keith, this glass is one of our own glasses I did a quick setup test on during the last order of glasses I did, back in July. I was curious about how it would last thru dishwashing too, so I had the wife put it in our dishwasher. She gave it back to me a couple of weeks ago, after 3 or so months. Looks just like it did when it went it!

The wine bar says their dishwasher doesn't hurt 'em either. And they came back for 500 more... ;)

324226

[Keith Winter]

Nice work landing the job Kev!

[Hilton Lister]

I use straight dish washing liquid or only slightly diluted and 2 passes at high res and power. The second pass removes the loose shards and scaling. I used to mask, laser, then sandblast. Before that, I used to use vinyl or washout mask and sandblast, but customers don't notice the difference, unless the result of the 2 different methods are displayed side by side. I despise using the sandblasting system and the extra time it takes to complete a job, even though the finish is nearly always superior. The laser fine works for me and I have decided I'm not going to waste any more glasses or time experimenting when the market won't bear the actual cost of sandblasting one off items.

[Jack Clague]

My Rotary was having a few issues so Trotec are replacing it for a new one, when I get that I will do a few more tests but probably settle on a decent setting that works well for my machine and my working temperature.

Thanks for all the input guys, this has been a great thread for info

[Bill Cunningham]

I use a coating of my own concoction, and never have a problem with glass whether I'm doing photos or text. One of my methods is posted on here about a year back, Cosby would be proud, and no, its not a roofee ;=)

[Mayo Pardo]

"Cosby would be proud"

Don't tell me - the secret coating is Jello Pudding Pops???

[Steve Oxenreider]

For those saying the paper won't have an effect on the beam:

I used to operate a 4400w co2 laser cutting steel. A STICKER left on the steel would totally blow my cut quality, sometimes it wouldn't even cut through. You can't tell me these lasers aren't effected by paper when that beast of a laser was.

[Chris DeGerolamo]

Man this popcorn is good...don't mind my crunching...

[Neville Stewart]

Use wet paper if you want " sanded" dont if you want " chipped".

[Martin Boekers]

I do a fair amount of JDS Black Mirror, front engraved... I find that just the industry standard masking works very well. Washes off easily with water.
The etched area is smooth to the touch and about 20% "Whiter" for a nice even contrast. I don't use and masking on glassware as it's hard to apply
evenly and sometime catches the wheel on the rotary. If you never tried the black mirror, give it a shot it's a nice material...

[Bryan Spiegel]

Something to add... in a different direction. I had trouble getting consistent quality on glasses for a friend's wedding, so what I ended up doing was coating them with plasti-dip, and then using etching cream. Rinse off after, and peel off the plasti-dip.

(Plasti-dip even featured us on their FB page for coming up with that plan of action)

[David Somers]

Scott,

Just curious. What you did you end up with for a sand blasting system? The last setup I saw was a micro sand blasting system by SMS and it did a beautiful job without consuming much space. Pricey little sucker however. In doing a little research I think you could do the same for far less money, but havent really dug yet.

Dave

[Bruce Clumpner]

So plasti-diy... laser... etch and clean? Just wondering how the cream got to the glass through the dip...

[Mark Ross]

The dishwashing liquid trick works on glass mirror quite well. But it has to be dawn brand, and only the blue stuff. The paper towel wet with water on top helps as well. However, use the cheap stuff, you don't want to use the stuff with the pillowing and ridges and this will cause issues. The cheaper the better. If you are going to use wet newspaper, do not use newspaper from liberal media sources, as they are already wet...lol...

Yeah any dish soap works. But trust me on the paper towel. I have found that there is also a difference in quality between glass mirror I buy at wally world, lowes, menards etc. When I found a good one, which wasn't the cheapest, I stuck with it.

Oh yeah, and only use bottle Evian water to wet the media, because we all know what Evian spelled backwards is, and yes, that is the inside joke on how they named it.