Doug you was talking about other paints with primer. I checked last night and the flat white I picked up the last time has the primer. This one was the outcome the last time I burned on tile over the ones I showed last night. Some day I hope to have a shop that looks like Andy’s …that is what I’ve pictures. Projects for days and time with the grandson 
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Very nice! I was quite surprised how different the two white paints came out when I first did my tests. Luckily one of the two was the right one and I got some good contrast. I did do a heavy coat once and found it was not nearly as good as one light coat. Such a cool technique and the fact that it’s permanent is mucho bueno.
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I wonder what makes so much of a difference by adding a thin top coat like that over just burning the tile. Why would it intensify the burn?
No idea how many trashed tiles I have in the corner trying to get something that looked ok.
It has to do with how the paint burns and sticks to the damaged tile coating. Like the Cermark stuff Travis mentioned to mark metal. But even there, with metal, there’s not enough power to do anything to the bare metal but certain chemicals, when heated, react with the heat and the metal to leave something stuck to the metal.
With the paint, I think too much and the chemical reaction is different and as we’ve seen, different chemical mixtures(paint types) have different reactions with the heating from the laser and the tile surface.
But that technique, thin white paint on white tile, is completely different from the multi layer technique where you are not only burning the paint and changing its properties(color) you are also exposing the colored layer beneath. AKA Sgraffito technique.
It would be interesting to find out exactly what chemical and chemical reaction is taking place though.
I showed that tile to Travis but never thought about the paint until you spoke of it. Someone on the Ortur group have talked about the primer some time back and that’s when I got it. I would have to look in my log to see what the final burn setting was.
There are lots of goodies in this thread( Ortur Diode Laser Testing ).
and tons of video’s on how to use Gimp to improve photos for engraving. Like this one for setting contrast: https://www.youtube.com/watch?v=Y-0ZcuhCsAU
And this one goes into lots of other editing techniques you can use in GIMP. I have to try the histogram one as it looks awesome! https://support.glowforge.com/hc/en-us/articles/360033633514-Prep-a-Photo-Engrave-in-Gimp
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Good looking out! Thank you
Tom, it is Titanium Dioxide pigment which gets burned into the tile as it burns through the glaze. This not only makes it permanent but also darker.
While I have good results with the Rust-Oleum 2x Paint+Primer I’ve seen others say they like the water based Rust-Oleum Zinsser Bullseye 1 2 3. I don’t strip the white paint off but others do an you need acetone to remove it so cleanup is work but the water based stuff is supposed to be an easier cleanup. YMMV.