There is a multitude of different printing processes, and even today new techniques are invented. Examples of new processes introduced only a few years ago are ink jet printing, laser printing and water transfer printing (WTD), which helps to address the still difficult challenge of printing complex spherically curved surfaces. Classical printing techniques, some of which have been used for centuries, are letterpress printing, stamp printing, offset printing and lithography. All of these are essentially limited to flat surfaces. Currently, the printing processes frequently used for moulded parts are screen printing and tampon printing. All these processes are based on the transfer of a print motif onto the surface of the object to be printed. Good adhesion to the surface is the precondition for a good print quality. However, there are also printing processes which are based on the fact that changes occur within or below a surface and are therefore not dependent on good adhesion to the surface. These are for example thermal printing, sublimation printing and embossing processes. The advantage of these processes is that they are not dependent on an adhesive bond on the surface and will not necessarily be damaged even by abrasion. However, these printing processes can only be used on particularly suitable materials. For the majority of printing processes based on the transfer of inks onto a surface, good ink adhesion is the prerequisite. Generally, the same requirements as for painting must be met in terms of surface energy and wetting..