The influence of preparatory layers on the stability of oil paintings is a subject that has occupied the minds of many authors of artist’s manuals, recipe books and related historical sources. Depending on their location in time and space, artists have had different views on the subject and have selected different materials and techniques to prepare their support for painting. Preparatory layers influence the texture of a painting, the colour has an impact on tonality of the picture and their absorbency influences painting technique chemistry. They co-determine the ageing and degradation of the painting. Because of these facts, the technique and materials of preparatory layers are of interest to many. For conservators, information on the layer structure - their composition and the degradation of their materials are particularly important. A good understanding of the intention of the artist and the original appearance of the painting is also necessary, since these influence conservation decisions.