Cool
20mm is odd sounds like a Jura random length either beige or grey/beige.
It’s not easy because the grease out of the sealer remains on the surface as it absorbs very little and dries slow if you’re not careful.
Lay it, grout it you will have no worries grout will slide off, when it is dry wipe the surface with a stain stop like lithofin. Use a fluff/lint free cloth like the stuff that comes on rolls for cars. Wet the clothe and wipe end to end 1 tile at a time until you get the hang of it. You don’t need to soak it and you don’t want bubbles.
When it’s dry it may look slightly dull but if you draw your finger over it will leave a shiny mark your wiping the grease off.
2 choices buff it and you may not get it all off leave it as the grease diminishes the more the floor is washed
Think that should do it if not pm me
tiler
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