:rofl2: , indeed, my German translating skills aren't all that; keep the stone free from oil and grease would be a better translation.
Coticules are non-porous, it's not an issue tbh. I know a lot of people that used theirs with oil in the past and I can understand why also.
The ones I were gifted were much finer and better finishers. Very well filled with oil and swarf.
Though, if you give them a quick lapping they're brand new, it's not getting deep into the stone at all.
With more porous stones, you're probably effed.