First attempt(s) at white tile

I’ve been reading and staring at images for the past few days. Finally tried a few runs at lasering a basic white tile, and I have a specific question that I think will only be served by seeing a picture.

Setup info:
Much of the settings you can see on the tile, but other setup info:
Hardware: Roly 10W (love this machine!)
LightBurn Material Test
Spray: Rust-oleum Painter’s Touch 2x Flat White
Text Setting for labels varied in my tests, I believe this specific one is 30mm/s 60%,
but I know 40mm/s 70% had a similar result.

I’m still trying to hone in on the right numbers (and spray material and coverage, etc.) for the squares, but I’m bothered by the label text itself, which isn’t just a matter of being too light/dark, rather it’s blotchy. Inconsistent at the level of even a single character.

What I’m wondering is if there’s something obvious that can shortcut me from spending another weekend messing with values and burning up tiles. Like maybe I didn’t get enough paint sprayed on? (2 light-med coats, one with horizontal passes, one with vertical), or maybe my settings are so far off that maybe that’s the problem. I just haven’t seen this kind of problem in my readings here.

(Never mind the yellowing at the top, that’s an artifact of the photo)

I’m currently working with the exact same paint on tile.

Same coverage, one full coat left to right, let dry for about an hour, then another coat top to bottom.

I get excellent black with 10mm/sec @ 30% power (10W optical power)

You may need to up your power on the text layer for the test. The lines you see are reminiscent of the marks left my the machinery that moves the tiles around the factory.
Did you clean the tile surface well (I use acetone)?

Seems similar. I didn’t wait that long between coats, it was a warm day outside (sprayed in the shade), probably only waited maybe 10 min for the first coat to look healthily dry, then did 2nd pass.

I can try to bump up the power, though if I understand laser power 30% at 10mm/s isn’t enormously different from 60% at 30mm/s. I mean maybe 2x, not like an order of magnitude, and within the range of my grid. The range of numbers I’m seeing other people having success with has quite a wide range. But perhaps slowing it down will help. I have another batch of tiles that I’m getting ready to prep.

As for cleaning, my initial pass was just with fine cloth, but the final pass was with 99% isopropyl alcohol. Is that not good enough? Anyone?

A little follow-up on this. I always appreciate when people wrap up their questions/discussion with more info, so here it is.

It turns out that in this case I was totally overdoing it. Based on Brewster’s comment (thank you) I went back and tried another matrix of lower values and it was substantially better. After honing in a bit more, at the moment for lines I think 8mm/sec at 20% power is going to be close to my optimum for these ceramic tiles.

For grayscale images I’m still not quite where I want to be, but vastly closer than I was a couple days ago. Here’s a decent one (though it’s from a stellar photo found online):

FWIW, I didn’t do anything fancy with the prep, no mixing my own titanium dioxide even, this is just Painter’s Touch 2x. I did wait longer between coats, maybe 45 min, and I waited overnight after the 2nd coat before engraving. I’ll experiment with other brands later, but all-in-all, for my 2nd tile out of the laser I’m feeling pretty good.