WITH PETER PAUl:. RUBENS (1577-1640) we corne to the last major transformation of the medium. The changes he brought about in the medium of the later Italians converted it into the most facile and versatile vehicle that any painter has ever had at his disposal. Technically, there seems to have been no limit to its possibilities and Rubens himself, with the freedom of execution that it allowed him in combination with his own great genius, reached the peak of pictorial realization. No painter has ever enjoyed a greater or more lasting renown. During his life his atelier had a tremendous reputation, and from the time of his death until our own time, painters of all schools have tried to rediscover his lost secrets; they have copied him-from Antoine Watteau (1683- 1721) to Paul CÚzanne (1839-1906)-in their efforts to learn how to paint.
Before we attempt to trace the various steps that led to such a high development, let us examine some of the qualities that distinguish his work and try to see in what ways his technique differed from that of his predecessors as well as of his followers.
In the Introduction, we have already described the method of examining a painting by means of the raking light and we will now see what this study reveals of the actual materials and methods of Rubens.
From Van Eyck to Brueghel (the Elder), the reliefs that stand out in the paint in this raking light are to be found principally in the light weight pigments-the blacks, browns and lakes-whereas the heavy pigments, because of their weight, have sunk toward the canvas and left hollows. It is exceptional, for example, to find a relief in the whites, on account of the density of this pigment. These dense whites formed thin layers but they have great covering power and are very bright. They have very rarely preserved the striations of the brush stroke. When we examine the paint on the