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. Contents: In memoriam: Karin Groen Introduction: Perspectives on the evolution of science for art history and conservation, and its current state Part I - Grounds and binding media Chapter 1 - Halcyon days for art history Chapter 2 - Grounds in Rembrandt’s workshop and in paintings by his contemporaries Chapter 3 - Earth Matters. The origin of the material used for the preparation of the Night Watch and many other canvases in Rembrandt’s workshop after 1640 Chapter 4 - In the beginning there was red Chapter 5 - Investigation of the use of the binding medium by Rembrandt. Chemical analysis and theology Part II - Changing colours Chapter 6 - Towards identification of brown discolouration on green paint Chapter 7 - Towards identification of brown discolouration on green paint revisited Chapter 8 - The foliage tends almost to blue Chapter 9 - Scanning electron-microscopy as an aid in the study of blanching Part III - Study of painting techniques Chapter 10 - Frans Hals: a technical examination (Co-author: Ella Hendriks) Chapter 11 - Judith Leyster: a technical examination of her work (Co-author: Ella Hendriks) Chapter 12 - Scientific examination of Vermeer’s Girl with the Pearl Earring (Co-authors: Inez van der Werf, Klaas Jan van den Berg and Jaap J. Boon) Summary Samenvatting Bibliography Acknowlegdements