There is no strict requirement for graphic companies to add ink, as long as they bring their own seals.

Stamps are used as stationery printed on documents to indicate identity or signature. Generally, seals should be dyed with pigments before printing. Those that are not stained with pigment and will appear concave and convex after being printed on a flat surface are called steel seals, and some are printed on wax or wax, or wax prints on envelopes.