In the group of drawings exhibited, the most widely used graphic medium is natural red stone or sanguigna or hematite; a pigmented clay containing iron oxides that in various proportions determine the colour (fig.1).
The group of drawings from the so-called Taccuino Corsini are all executed on prepared paper with a pinkish hue and the sanguigna strokes (from the extensive use of sanguigna stone as a drawing technique) insist more or less vigorously on this background colour, where lights are sometimes ‘raised’ with chalk and some contours are emphasised with black stone. This pinkish background, as attractive as it is irregular, is not in fact a ‘preparation’ in the sense in which a prepared paper is technically understood, i.e. a sheet of paper on which a binder, a filler and a pigment have been spread, all prepared to receive and return the trace of metal points. This is in fact a ‘spurious’ form of preparation, in which sanguigna is pulverised and applied to the white sheet. The traces of brushstrokes are visible on the papers, but not the consistency of the preparation as such; in fact, the paper and the layering are still legible under the light drafting similar to watercolour.
The extreme solubility of sanguigna, which in contact with water undergoes the dispersion of ferric oxide pigments, makes this technique extremely versatile: by moistening the point with water or saliva, a more compact and darker stroke can be obtained, thus achieving a strong accentuation.
Black stone is present in the exhibited sheets to a lesser extent than in the artist’s overall production and always, in our case, in combination with sanguigna (fig.2).
A privileged tool for Renaissance drawing, it appears in studies, cartoons and preparatory drawings and was used by Pontormo, Raphael and Michelangelo.
Vasari speaks of a ‘black stone from France’. It is a carboniferous clay schist, with a less labile stroke than charcoal, which could ensure a freer and more vibrant style than metal points.
Finally, white chalk emphasises the effects of light (Fig. 3). There are many varieties of it in nature with different compositions; it is characterised by its powdery trace, evident in many of these small sheets, which is susceptible to rubbing and excessive moisture, and tends rapidly to become blurred and lost. Several types of natural chalk are known: tailor’s chalk or steatite; scagliola, which when wet and formed into sticks can be used for drawing; ordinary chalk or chalk and white stone.
It is precisely in the nucleus of Corsini’s origin, now exhibited for the first time in its entirety, that the different applications of a precious and personal creative workshop emerge clearly: functional drawing and autonomous drawing.
The various phases of the graphic elaboration of the work to be realised reveal the different states of the preparatory drawing, from the sketch or rough draft, closely linked to the search for the formal definition of the work itself, as in the small composition for the Sacra Conversione (Pala Pucci, 1516 – ante 1518) in the church of San Michele Visdomini, and then moving on to the squared model, as in the Saint Cecilia executed for the lost fresco in Fiesole (c. 1519) and the Study for the portrait of Ippolito de’ Medici, preserved in the Uffizi (c. 1525), characterised by the development of a precise composition that would serve to transpose the drawing to scale onto the surface to be painted (figs. 4 and 5). Pontormo used cross-hatching both by tracing it with a stylus and by using sanguigna).
