Advice on Metals and the Glowforge

Hi there GW Fam.

I want to ask some novice questions regarding engraving on minerals such as metals and stones.

I’ve seen some people engrave on stainless steel knives and metals as well on “Anodized Aluminum”. I’m completely terrified to do experiments on my own due to my little understand of metals and reflective surfaces. I know that using a laser on glass is 100% not ok since it will bounce off and be no good, and because of that I don’t know if that applies to “reflective” surfaces as well. (I.E. a very reflective knife, or piece of metal) Is it the same thing?

Has anyone tried to engrave on stone? Like flat round rocks that you find on the beach? is that possible? On the Glowforge home site I do recall engraving on stone was a thing that was mentioned. Is this true or am I remembering it wrong, I’m also afraid to try this as I tend to be very careful with what I put into my laser.


Yes. There are examples of stone etching on this forum

Hmmmn. okay you’ve got some misinformation in there.

Glass is perfectly safe to laser on with a CO2 laser, (which this is). You can use the laser to engrave the glass, but you can’t cut through it. (It’s like hitting a brick wall for the laser, it won’t go through.)
When you engrave it, the heat from the laser will just chip away small bits from the glass, and there are tricks to keep the heat from cracking it. You can look up engraving glass in the Beyond the Manual section. A lot of people have done it successfully.

Engraving on stone and slate is very safe - stone doesn’t burn. What it does do is throw a VERY BRIGHT LIGHT that is going to be too intense to look at directly, so don’t try it. You will burn spots into your retina that will take several minutes to clear. (I’m not kidding.)

There are settings for engraving slate and stone in the Beyond the Manual section as well. It’s the only section of the forum where we are allowed to post specific settings information. So you can look that up there too.

Same for Anodized aluminum and metals. There are settings and techniques there. (And if you are concerned about reflections, you can mask the material before engraving/marking it.)

It’s a great idea to check what other folks have tried before jumping right in…Good for you! :grinning:


Can confirm, you can burn the bejeezus out of stone with no significant danger. (It can get awfully dusty, though.)


Yeah, same with eggshells. Powder everywhere.


Ill take rock dust over rubber ash! That stuff is a nightmare. :stuck_out_tongue:


So i hear…haven’t tried it yet. :slightly_smiling_face:

Was this engraved with the GF? Some of those “B’s” look super deep how did you do that?


It’s the only laser we have. :slight_smile:

IIRC, all the engraves are at full power, with speed increasing from left to right. Number of passes increases from top to bottom. (So the utterly destroyed B at the left of the third set was 100 speed, full power basic, 3 passes.)

The two sets of white letters were cut through painter’s tape, then painted and the tape removed.

The material is a cutoff from a countertop fabrication shop. We got a fair variety of scraps from them. Some were much softer than expected and engraved well, while others we could barely scratch.


only metal I would stay away from in Galvanized metal as it will emits dangerous fumes (Zinc fumes are poisonous and also reason why you dont weld on it


Copper is a real problem as well apparently as of all metals it is the most reflective of the wavelengths of the CO2 laser and thus the real “mirror problem” that could damage your machine. I only learned it in this forum, but from folk more knowledgeable than me.

So I want to be 100% that I am understanding what you are saying.

  • I can engrave on Mirrors without any damage to my machine?

  • I can engrave on Stainless Steel Reflective Surfaces without any damage to my machine?

I’m not taking your word as gospel nor do I want to put that on you, rather I just want to confirm.

Are there any other metals aside Galvanized and Copper that I should definitely not be playing around with that would be toxic?

I have an 11 month old daughter and It would kill me to know that I harmed her because of my experiments and the like.

As far as I know both of those are okay. (But please do look them up in the Beyond the Manual category - there might be a trick to dealing with mirrors that is different from dealing with plain glass, which was what we were discussing before.)

You can always burn the backing off of a mirror to create a pattern in it, and there will be no reflection issues, or apply some paper masking to anything you have questions about. (Or just use mirrored acrylic - the results are just as nice as a real mirror, and less chance of breakage. Gonna stink though.)

And no copper. And no PVC plastic or vinyl.

The reason that most metals / reflective materials are safe is because the beam NEEDS to be focused to have sufficient power to do any damage (or in the desired case cut, engrave, or score). Once the reflection occurs, not only is part of the beam energy absorbed, it is also dispersed making it more and more harmless as it gets further from the material.

You want to stay away from copper and from chrome plating because they are reflective to the wavelength of the laser. Some people think that a reflection would be too diffuse to do any damage to the inside of your laser. Personally, I don’t see any benefit that would outweigh the risk. Chrome-plating is not super expensive, but it is also not cheap, so while I doubt many mirrors would use it you may want to verify.

Anything with chlorine in it should be avoided because the gas released is very, very corrosive to the insides of your glowforge. PVC (think the white tubing used in plumbing and vinyl) is the biggest no-no, but if you think it may contain chlorine best to not try. Also, the gas is bad for you and your lungs, but I’m not sure how you’d get a good whiff of it in a properly ventilated setup.

The gas released from cutting chrome-tanned (also could be referred to as oil tanned) leather may contain small amounts of hexavalent chromium a known carcinogen. It would appear that the amounts released from normal cutting would be considered safe by OSHA for an adult, and if vented there should be no risk, however, it is perfectly understandable to play it extra safe with your newborn. Please note this does not apply to leather that has been vegetable tanned.

Now on to fun stuff. Yes, you can get deep engraves in stone, but other stones are barely marked. Travertine tiles, pretty cheap at places like Home Depot/Lowes, can be engraved pretty deeply. I did some and found if you go too deep after a few weeks a talc-like, slow motion eruption may occur and crack the tile. But that was pretty deep. It has been 4.5 months since I made some coasters with a just right depth of engrave and they have been fine. As for other metals, some mark pretty well and others are pretty resistant to change. You just have to try and see. One thing I have read here, is that for anodized aluminum you have to be very precise in the measurement you enter in the focus height for custom material to achieve the best results.


That would have to be a chemical reaction to oxygen or more likely water vapor. It would be interesting to learn the chemical content of the “talc” but more interesting perhaps if a spray varnish or other way to limit the chemistry would work to prevent it. It seems pretty obvious that you create an endothermic reaction that reverses, and is larger volume than the precursors.

Presumably whatever travertine is.

Travertine is limestone so the “talc” would be calcium as the heat would drive off the CO2 and whatever water was attached, recombining the calcium would seem to be a different phase structure as would need to be to cause the expansion. How that would happen specifically perhaps somebody here could explain as I am frequently amazed at the general knowledge in this group.

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