Preliminary drawings beneath the surface layers of a painting can often be made visible by a technique called infra-red reflectography. The fascinating revelations of such underdrawings are always a source of important material for art history, leading to deductions about attribution, style, changes in composition, and workshop practices. This volume presents the results of pioneering research on the underdrawings of 15th- and 16th-century paintings by conservation, scientific and curatorial staff at the National Gallery in London.;The contributors to the book explain the techniques of infra-red photography and reflectography and discuss the materials and technical findings of underdrawings in paintings of the Renaissance period. Also included are detailed entries on the underdrawings of specific paintings by such renowned artists as Raphael, Giorgione, Cranach, Altdorfer and Bruegel.