Originally Posted by
Euclid440
Yes, exactly.
When I lap a new stone I grid it several times 4-5 spinning the stone 180 degrees, with each grid layout and lap from corner to corner and end to end.
If you lap a stone where you are raising a lot of slurry, that slurry alone will remove the pencil grid, especially if the grid is applied lightly.
I noticed this when lapping natural stones with loose grit. So I started marking hard natural stones with a sharpie, with is not as easy to wash off.
Once the stone is flat, you can quickly remove a new pencil grid, so it is not like you are endlessly lapping the stone. I also lap with progressively higher diamond plates, just draw a quick grid to make sure the stone is flat.
If the stone is flat, one lap up and down will remove the grid, completely. If you see low spots, that part of the stone has never touched the plate and will be much rougher than the lapped part.