The care and repair of works of art, broadly known as art conservation, is an activity as old as art-making. Art objects grow old, and while some last for centuries, others last for only a few years. What makes some objects so durable, while others age so quickly? Can the aging process be slowed through careful storage and display? When serious damage has occurred, either through again or some catastrophic event, what can be done to restore the object’s former beauty? These questions lie at the heart of conservation efforts, and just as medical sciences have led to longer, healthier lives for people, conservation science has revolutionized the care of art objects. The "health" of material artifacts can now be described and monitored, and new ways are being developed for minimizing their deterioration or for restoring them with safe and effective materials and techniques. In large part, these advances have been made possible by scientists working in art conservation. This book is a compilation of the work of one of those scientists, Robert Feller, whose research stands among the most important contributions to this field. In this volume are collected the seminal and often definitive papers published by Robert Feller over his career, including many of his scholarly studies and explanations for lay audiences that originally appeared in books, journals, exhibition catalogs, and trade magazines. Ranging from his scientific studies of paper and paint deterioration, to his historical investigations of the color wheel and the various spellings of "damar" varnish, these works have formed the basis for the enlightened care and repair of art in our day.