For more efficient and energy-saving drying of ink and/or coating films in printing machines, the drying or hardening process must be better monitored. Therefore a method is proposed for determining the degree of hardening of one or more printed ink and/or coating films on a substrate that was coated in an intaglio, flexographic or offset printing process. The degree of hardening or drying due to the hardening or drying process is determined indirectly via the change of mechanical and/or viscoelastic properties of the ink and/or coating films on the substrate. An ultrasound measurement is used for this purpose.