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The rheological behaviour of 5 water-reducible flexographic printing inks was tested using viscometer with the cone and plate geometry. The obtained shear stress versus shear rate curves for the original inks, and additionally, for the mixtures with various amount of added water, exhibit pseudoplastic behaviour, and were successfully fitted by Ostwald and Casson models. The viscosity of printing inks after addition of water was tested also by means of outflow funnel. The transfer of flexographic inks on the different paper substrates was examined by optical density measurements. The density curves confirmed that the ink concentration above 50 wt% is sufficient to obtain the constant value of optical density. The best ink transfer to the investigated paper substrates was observed for folding carton characterized by the high value of smoothness.