The goal of printing is to apply an image to a substrate by the application of the thinnest possible film of ink that will give the desired colour strength. Developments in equipment and in the production of higher quality Flexo inks has been helping the expansion of this process as a good alternative printing method to gravure and offset printing. The key to obtaining good UV flexographic inks lies in good pigment wetting, ink rheology and the reactivity of the system. Rheological behaviour with the correct amount of well-chosen pigment is directly related to pigment wetting. This imparts to the ink many different properties such as good dispersion, good flow, good transfer to equipment and substrates, correct viscosity, tack and print strength. Also of great importance is the final reactivity of the system and this will affect the choice of the resin. Only highly reactive resin systems may be used in this field.