In the study of the <i>Head of St. Joseph</i> (a fragment), a network of cracks and layers of varnish make reading of the underdrawing difficult. The drawing is purely linear and not very visible because paint was applied in thick layers on the drawn outlines. All traces of drawing detected by the author are reported and interpreted. For the <i>Head of St. Catherine</i>, also a fragment, the drawing is also linear with some hachures and some reworkings. Several are noted, and detailed observations on the differences between underdrawing and outlines of the painting are made. The most noticeable reworking involves the area of the eyes and a change in their direction is noted. -- AATA