Help with engraving photo on granite

After seeing the success stories here with engraving on granite, I’m trying to do the same. We have some good friends who recently lost their beloved dog, and built a grave for her at their cabin. I want to give them a granite tile with the dog’s photo engraved on it, along with her name. So I bought some granite tile to experiment upon, and went to work using the settings I’ve seen on other posts (335 speed, 30% power, 270 LPI). Didn’t use masking of any type.

What you see here is the result. I’m also posting the image file I’m using, which was processed in Photoshop and halftoned, since I’ve never been able to get decent results with just grayscale. I’ve made this image look good on slate, but that’s not a good option for an outdoor gravesite that’s hot in the summer and frozen in winter. Gotta use granite.

I realize that granite is a much more “speckled” type of rock than slate, so there’s going to be some loss of photo detail on my final product. I can live with that. But I’m bothered by the banding I see on her neck, and also below her eyes. And if you take a close look at her face, it seems to me there’s a subtle banding across the whole thing, almost like what you get from an inkjet printer with nozzles that aren’t quite aligned. I was doing some engraving on wood the other day, and it came out fine, so I don’t think it’s an alignment problem with the GF itself. But while I’m no expert on granite or rocks in general, I have to question whether the banding would be so straight if it was an issue with the layers in the rock. Could this be a problem with my LPI setting? Maybe I have to adjust it a bit one way or the other?

Any thoughts or advice would be appreciated.


So with LPI and whatnot, the issue you’re referring to is unwanted moire patterns in the dithering, yeah? If that were the case I would expect to see the bands cut across the entire art, and you’re not seeing that. I think this is just inconsistent material.

Take this marked up version:

So the red rectangle is your discoloration… I think there is a band of area in the material that continues to the right in the yellow area that looks visibly different. I think maybe that’s down to something about the way the stone was manufactured/formed.

You can see some other suspect areas with the red arrows at top.

As for dithering patterns, you can see it a little with the blue arrow in the ear. The exact greyscale of your image and the dithering algorithm made a bit of a pattern. It’s going to happen in almost any dithered job.

So, as for how to fix it? Sometimes you can overpower slight differences by giving the laser some more power or less speed. Might be worth a few tests, but if the material is highly variable then it’s tough to get around it (like in bamboo engraves, notorious for material inconsistency and banding).


Thanks for the input. Nothing would make me happier than to think it’s the material’s fault instead of mine. What would be your thoughts on how much more power to give the laser?

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In general, stone can take a lot of power, but you can get an effect where the surface is so cracked that the engraved area can flake and look uneven.

An example:

Your best bet will be to test a bit, people might recommend settings but your stone isn’t exactly like anyone else’s. Other glass/stone posts can give you a general idea, but overall I’d say you look like you’re already in the pretty good range… your engraves have good contrast, it’s just uneven on that material. It’s hard to say, and testing is really the only way to be sure.


Well, I’m not sure why, but upping the speed and power seemed to do the trick. This one was at 1000 speed, 60% power, and 270 LPI. I did another one using the same speed and LPI, but only 50% power, and it was a little too dark in some areas. This one might be just a touch too bright - some of the fur details aren’t very clear - but I think if I knock the power down to maybe 55% or so, I’ll have a happy medium. Thanks for the advice!


Here’s a final update that will hopefully help others in the future avoid some of the mistakes I made during this process. At the very least, it should provide a good starting point for your settings.

I was happy with my last test, but not totally satisfied. That nagging little voice you get that keeps saying you could have done better. The problem was, my test results were very inconsistent. Photos on one setting would come out too bright, but when I’d adjust laser power by an amount as small as 5%, the image would barely register on the granite. Then I’d try again on a different piece, and get a whole other set of results, but no consistency. It wasn’t making sense that the results of such small adjustments were so all over the place. I knew it wasn’t a fault with the machine, because other projects (on wood) were coming out perfect every time.

My original piece of granite was a tile purchased at the local Floor and Decor. I went elsewhere and purchased a box of highly polished, “Absolute Black” 12” x 12” granite tiles, which looked a LOT better (if you’re going to engrave granite, use this kind!). But my test results were still inconsistently wonky, and I just couldn’t pin my settings down.

Then I had one of those facepalm moments that made me kick myself for not thinking of it sooner. The vast majority of my projects are on wood or MDF, both of which are bright, flat, non-reflective surfaces perfect for auto-measuring thickness with the Glowforge’s built-in laser. But I started thinking that granite might reflect the laser much differently (obviously this post is for amateurs like me, not all you pros reading this and saying, “brilliant observation there, genius”). With its black, highly reflective surface and the crystalline nature of the rock itself, maybe the GF laser wasn’t getting an accurate reading every time. So I pulled out the digital calipers, measured the tile thickness (0.42”), and fed it into my settings manually instead.

Instant, consistent results! After solving that issue, it didn’t take me long to play with the settings until I got it right. The photo you see here was engraved at:

1000 speed
45% power
195 LPI

40% - 45% seems to be the magic number for a halftoned image like this. Your individual mileage may vary depending on the photo itself, but this is a good starting point. I did an engrave at 35% power, which had maybe a little more detail in the neck hair, but was overall too dark for my taste.

Hope that helps someone in the future, and thanks again for the feedback.


This looks perfect, in fact it’s the best that I have ever seen. Well done. :blush:

Sometimes for really shiny surfaces, I pick a flat patch that won’t be engraved and I put a small square of masking on it, just to give the laser a spot to focus on while measuring.


Quick question. I have a memorial to do as well, however it won’t be a photo, just an svg file. Do you think that the settings you used for your final image shown would be the best for that as well? The last photo shown came out beautifully!

I’m assuming that by “SVG file” you mean that whatever you’re engraving will be basic black and white line or text - basically line art with no shades of gray. If so, then yes, the settings I listed above would work. But if you don’t have to worry about shades of gray, maybe bump your power up to 65% or so. It’ll make your engraving a little brighter against the black granite.

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Yes, just lines, black and white. Thank you so much! 2nd day using machine and very unsure of what to do. Sure don’t want it to get ruined! I have a scrap that I can use also to test. Thank you again for your help!

There are any number of things that might ruin your GF, but engraving granite isn’t one of them. The laser isn’t anywhere strong enough to make the granite smoke or catch fire, so have fun with it. For me, it’s a relaxing change of pace from my usual wood/MDF board projects.

And if you’re a GF newbie, the best advice I can give is to keep these forums bookmarked! When in doubt, ask questions. This is somehow the one non-toxic corner of the internet. Too many other forums are full of people who love to post snarky, unhelpful replies, or call you a dope just because you asked a basic question. Not here. Post a question here and within 24 hours, you’ll likely get two or three solid, knowledgeable responses on what you should do next. This forum is a huge resource. Use it, and have fun!


Thank you so much!! I’ve gotten to where it’s taken me more than 6mths to use the machine as most of the time, people are just awful and truthfully, it wasn’t worth the stress of dealing with nastiness just because I don’t understand something. For whatever reason, this seems to be the one thing I cannot comprehend, not sure why, but I have really struggled. Partly due to having so many different ways for the settings. I downloaded the doc sheet with materials and settings listed, but seems that’s a 180 with the FB groups I’m also in, so the learning progress is much slower for me. I’m plugging along though and so appreciate folks who help!

I also drop in on the GUG Facebook pages. It’s good to see what others are doing and saying once in a while, but if you want the most knowledgeable and reliable information about anything Glowforge, this is the place to go. It has been around for over 6 years with an unbelievable group of people who are eager to help you and will never intimidate or embarrass you in the process. The Facebook places are often sources of misinformation. Make this your go-to place, first. Have fun!


Thank you! I am trying to learn fast! I am just so appreciative when someone can explain something and I can actually understand it lol!!!

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Thanks for sharing. This is very helpful. I have been trying to engrave my dads photo on his grave marker but I have not been able to get the photo as great and detailed as yours…UPDATE- I just retried your settings (using same material) and it made a words of difference. Thank you, thank you, thank you so much for sharing.

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Glad to hear it. I haven’t had occasion to engrave anything else on granite since I posted, so I’ve been wondering how those settings might work for someone else. Photos are tricky, and half your battle is just going to be processing the image properly before it even hits the GF. GOOD LUCK!

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