A non-flowing protective medium is applied in a finely distributed manner through a metering nozzle by means of blown air to the non-printing regions of at least one roll of an inking unit or damping unit and/or the non-printing regions of at least one transfer cylinder or forme cylinder, forming a thin-layer protective film. Ink is thereby prevented from drying out in non-printing regions of the rolls and cylinders of the printing unit, and the tack is thus kept at a low level, in order to reduce the risk of web breaks.