That would be my guess. The wavelengths are radically different than the CO2 laser we’re using. I’m not certain it is a heat issue as much as the wavelength of the light that’s doing it.
A quick test would be to use a clothes iron or soldering iron to see if that turns the paint black.
I’ll be doing some in depth tests tomorrow so we’ll see.
The backing on the glass tiles seem to do this now.
It’s a treasure hunt! 
That is a stunning image, and result.
I wonder if the white matte paint is a red herring, and maybe what is actually going on is something like @bwente seen in their post here.
It might explain why his coating is so durable at the end of the video resting the scraping.
Edit: Sry didn’t see you had mentioned it there.
But in the video posted here it look like a regular ceramic tile. It is strange. The glass tiles are odd ones.
I was trying to go frame by frame and see how the reflections carried across the dark sections but the 360p is holding me back hehe. Could also be some strange reaction with the paint and glaze? I found the paint used at least so if my local hardware stores carry it i will test and post my mistakes. I need to build an urn for my parents yorkie that passes away and something like this would look better than the slate in my moms opinion.
I’m sure you all have found it as well but just in case here it is Here
I think it is Audrey Hepburn that makes the difference. I bet Mother Teresa would work too!
Was looking at the sds of the paint and this is what came up. not sure if this is the exact same stuff but i clicked on a few rustoelum white paint sds sheets and they appear to be the same recipe for the flat white finish. Here
Oh and be careful what rabbit holes you fall down otherwise you will look up the sds of cermark spray and paste to find out that the spray has something called “DOCUSATE SODIUM” so you google that and then find out that it is a stool softener 
And then you forget what you were searching for in the first place and finally go to bed.
You could always power down enough to not turn it white. It probably either drives carbon into the glaze though If you can make your own glaze it might reduce it! It would be interesting with a glaze with a lot of iron.
Well… I think everyone needs to look into this deeper. My first settings test was pretty successful.
From bottom to top… 1000 zooms and 20 pews… 500 zooms and 20 pews… and 250 zooms and 20 pews.
Obviously that was the best of the bunch. I’ll have to do some more tweaks and see if I can improve it from there. The first picture still had the flat white on the tile. The one directly above I had removed all of the flat white taking it back to the shiny white tile and nothing of the coloring was removed.
I then went beyond what the guy in the video did and took the CORNER of a paint scraper to it and I was really trying to scrape that crap off. Nothing. You can see some discoloration where I was really putting the scraper to it, but I would say that’s a worst possible case scenario.
Now I just need to find out if I can up the pews so I can up the speed… or if it HAS to be low power and low speed to get the job done. I’m kinda excited here. 
UPDATE: those lines on the image after I took the scraper to it? Rubbed off with my thumb. It’s like I never even touched it. That stuff is as permanent as it’s going to get. The only question is to whether it will fade at this point.
Thanks for testing this. The glass tile seemed lower and slower were better.
That was the set of three i had set up to put the most power to it as well. I had another set with the same speed but with 10 power and another set of three with 5 power. But at this point and from my first test yesterday, I think it’s the speed more than the power. But more testing will be needed before I can verify that. But I’m thinking real hot, and slow so the heat lingers is what’s causing the effect.
I’ll be back in an hour or 2 when this engrave finishes…
This is the image I was trying to create.
This is just after the print finished on the far right tile.
Wow…that looks pretty good. (You’re right, this needs exploring.)
Grayscale? I would have thought dither would give better results.
The high DPI probably helps, but I think you’d get darker results if you slow it down a bit. This is going to take a bit to dial in perfectly I think. But I’m totally impressed with the results I’ve (and you’ve) gotten so far.
