The essays in this volume address a range of subjects studied by the conservation division of the National Gallery of Art related to the Gallery’s collection. The first essay provides the properties of azo pigments, which are widely used in artists’ materials and commercial applications. The second investigates the frame elements and construction of a Trecento altarpiece by Agnolo Gaddi. The third discusses the conservation of a Renaissance polychrome and gilt terracotta relief. Next is a report on the results of x-ray fluorescence analysis that highlights a unique pattern in Matteo de’ Pasti’s casting materials of portrait medals. The volume finishes with essays on the painterly techniques of Kazimir Malevich and Jan Steen.