Draws attention to the necessity of a thorough knowledge of historical painting techniques for curators and conservators. Just as the anatomy of the human body must be known in order to understand its functioning, so it is necessary that one studying paintings scientifically, or the conservator who treats paintings, be well acquainted with the structure and materials involved. Methodical investigation preceding any treatment by a conservator is a prerequisite for the treatment to be justified. This investigation should involve aspects of material damage and its causes; aesthetic, material, and functional properties; craftsmanship; and traces left by the maker and by history. The same is obviously true for the art historian and his interpretations. Methodical investigation consists of a close interdisciplinary cooperation between restorer, art historian, and scientist and, next to the study of the object itself, of a sytematic research into and study of historical sources. Mention is made of the file system of historical sources of art materials and techniques in the Netherlands, developed in the Central Research Laboratory by Dr. Ernst van de Wetering. Work is being done to computerize the existing information retrieval system.