Slate finish

Hey y'all!


It was kinda surprising for me to learn that I can mark and engrave slate plates with my 30w fiber, even shades of grey are achievable. Thats great!
When you pour water on marked slate the marking dissapears, but comes back when the water dries out. No problem there. But oil/grease/fat is differenet. When I tried to pour oil on it, marking dissapeard and never came back, not even after cleaning with soap/degreaser/dishwashing soap. I must put some finish on it I figured... but that seems to have same bad effect of making the marked picture go black. I tried so many finishing transparent colors, lacquers, sprays... but every single one does the same - marking goes and stays black.


I saw this guy on youtube engravin/marking slate plates and than using some kind of lacquer spray and the marking stays the same whitish color. (video here: https://youtu.be/LbT8mkd7uPE?t=129). How can I achieve this? I kinda dont believe that using CO2 or fiber is the reason, but Im no expert.


Can anyone help me out with this? Is there some special kind of lacquer that doesnt do this to fiber laser marked slate? BTW, I tried to find the exact same spray as in the video, couldnt find it in my country :(

Any help would be much appreciated!