It is a recognized fact that the majority of the many drawings produced in the 16th and 17th centuries have been lost. It is quite likely that a great deal of these lost drawings were the work of aspiring artists, done for practice during their training. Written sources, so-called 'Tekenboeken' and pictures of studios give us some idea of what such drawing exercises looked like. Series of eyes, noses, mouths, hands and feet, etc. served as preliminary exercices. Although these were recognized as very difficult assignments, their great advantage was that a single glance, even that of the young draughtsman himself, could establish whether the task had been done well, because 'mistakes are generally evident and can be seen and judged by everybody: for who is so dull and blind as not to notice whether someone has a deformed face, a twisted hand or a crooked foot?' (note 8). One duly wonders at the total absence of such drawings in Gerard Ter Borch senior's large collection of work by his sons Gerard junior, Harmen and Mozes. Apparently Ter Borch père was more selective than assumed by Alison Kettering in her introduction to the catalogue of the Ter Borch estate. Of the earliest drawings done by the young pupils in their first years, he seems to have concentrated on preserving drawings done from life and the young artists' own invention. As for drawings after prints, only copies of complete compositions were apparently worth saving. One could surmise that such practice drawings were executed on carriers which could be erased or re-used in some other way. The making of such carriers from box or palm wood and also from parchment is described in Cennino Cennini's 'Il Libro dell'Arte' (ca. 1400). The replaceable primer that was applied to such carriers consisted of ground white bone-ash mixed with saliva. According to Cennini, parchment 'tavolette' were also used by merchants to do their calculations on. The use of such parchment tablets is moreover confirmed by an early 16th-century recipe from Bavaria. The question arises as to whether erasable carriers were only used by beginners, as Cennini's text suggests, or by fully developed artists as well. This might provide a possible explanation for the total or virtually total absence of drawings in the oeuvres of some artists. Another question is how long this type of carrier remained in use. Research was sidetracked by the frequent occurrence of young artists drawing on blocklike boards or planks, notably on title-pages of 17th-century books of drawing models. In 16th-century iconography such boards appear to indicate the term 'usus' or 'practice'. They also refer to a Pliny text according to which drawing on boxwood boards was a fixed item in the education of well-born Greek children. The depiction of young draughtsmen with such drawing boards may therefore not represent actual studio practice but allude to the aspired high status of drawing and of the art of painting in general. The very nature of erasable carriers means that traces of them are rare. Those boards that have survived (Meder had published a number) are not acknowledged as such apart from the wax tablets intended for re-use in Classical Antiquity, and in the Middle Ages too. There are sporadic references in written sources. Karel van Mander, for instance, uses the term 'Tafelet' twice, the first time in connection with Albrecht Dürer who - significantly in this context is said to have portrayed Joachim Patinier on a slate (the ideal erasable carrier) 'or a tafelet'. Van Mander subsequently mentions a 'tafelet' in his biography of Goltzius, who was asked to do a portrait on a 'tafelet' in preparation for a print. The very strong likelihood that the term 'tafelet' was used to indicate a carrier suitable for re-use is endorsed by a recipe by Theodore de Mayerne (ca. 1630), who suggests two ways of making a 'tablet à papier' for writing on with a metal stylus: strong and well glued paper is spread with a paste of ground bone-ash, not mixed with saliva this time but with a weak gum solution. To prepare the tablet for re-use it could be cleaned with a wet brush. When the paper had suffered too much from this repeated treatment, it could be varnished, according to de Mayerne, after which it could be written on again with a pen, washed off again etc. Although de Mayerne recommends this 'tablet à papier' for practising writing, no distinction was made between carriers for writing and drawing (cf. Cennini above). We shall probably never know to what extent erasable carriers were used, but the foregoing remarks may shed a fresh light on a group of works of art, drawings with silver or other metal styluses on prepared parchment or paper. Instead of resorting to one of the highly specialized and expensive drawing methods which are often cited, for example in connection with Rembrandt's portrait of Saskia in Berlin with silver stylus on prepared parchment, such drawings may have been done on tablets which were not intended to be preserved. Goltzius' portraits with metal stylus as a rule were executed as drawings which served solely as the basis for a print. From a text in P. C. Hooft's Warenar (1616) we learn, that a 'tafelet' or 'taflet' was a booklet used as a scrap book and habitually carried in the pocket. A few of such booklets have survived. One is a booklet with fourteen prepared paper pages which belonged to Adriaen van der Wcrff. In it, writing with a silver stylus, he kept a record of the number of days he spent on his paintings. The first four pages of the book were prepared for re-use. The traces of earlier inscriptions can still be vaguely discerned under the new layer of primer. A second tafelet - originally containing twelve pages - was identified in the collection of the Rijksprentenkabinet (note 41). It was used around 1590 by a young painter who practised in it by copying fragments of prints.