Since instructions on painting technique, provided by historical sources, are mostly fragmentary and unsystematic, this information is often difficult to interpret. In order to simplify the interpretation, it is proposed to categorize the instructions according to their function within the painting process. By doing so, it is possible to form groups of recipes which painters had at their disposal to obtain a specific aim with respect to painting techniques. In this way, fragmented instructions from divergent sources can be confronted and mutually explained. The present paper contains elements of the book the author is preparing on this subject.