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:
Coke without paper.jpgCoke with Paper.jpg

Image with a slight top down view on kitchen bench background
Left Focus without paper.jpgLeft focus with paper.jpg

Image with straight on view and brownish background
Straight focus without paper.jpgStraight focus with paper.jpg

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:
Coke without paper.jpgCoke with Paper.jpg

Image with a slight top down view on kitchen bench background
Left Focus without paper.jpgLeft focus with paper.jpg

Image with straight on view and brownish background
Straight focus without paper.jpgStraight focus with paper.jpg

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...