This book is a collection of scientific papers written over 30 years by Karin Groen on aspects of the painting of Rembrandt, Frans Hals, Leyster, Vermeer, Van Gogh etc. The author tracks the historical development of the application of scientific techniques in research into artists techniques and materials and examines phenomena such as the changing of green pigments to blue, the use of red in preparatory layers, binding media, blanching and organic pigments.