The quality of a stamp impression also depends on the choice of paper.
Not every paper can be stamped equally well: the imprint is more irregular on rough paper. With a smooth paper it is finer. Coated or sealed paper does not absorb the ink at all or only very slowly.
We prefer to use an uncoated, rather smooth paper, as is the case with our cards and paper tags.
Tip: Test your stationery before stamping large quantities.