This book presents a research related to the characterization and physical chemical properties of organic materials used in paint layers both from natural and synthetic origin. I focus my attention on proteinaceous materials used as binders in tempera paints, their interaction with coloured pigments and their ageing behavior, and on alkyd resins used in modern and contemporary art, in particular synthetic resins produced by the Winsor & Newton, series Griffin, Fast-drying oil colour. Also silane/siloxane coatings were studied and the selected product will be applied on the wall painting "Tuttomondo" of Keith Haring on the Church of Sant'Antonio in Pisa.