The enormous interest of the Prado’s copy lies in the fact that from the preparatory drawing to almost the final paint layers it repeats the creative process of La Gioconda without aiming to be an imitation of it. Comparative analysis of the infra-red reflectographs1 has revealed identical details beneath the paint layers that reveal a parallel process of elaboration. In the document here it can be seen that the figures are of the same size and shape and have possibly been transferred onto their respective supports using the same cartoon (see fig.8).
The preparatory drawing on the original is not as precise as that on the copy although it also has the lines that indicate how the figure’s position was shifted and the intermediary phases of execution that are also found on the copy (see fig.9). The brushstrokes that define the forms in the original also appear beneath the paint surface of the Prado figure, all slightly displaced. They are to be found on the figure’s back, waist, shoulder and hands (see fig.10), on the line of the breast (see fig.11), on the folds of the sleeves and on her lap.
Some of the lines of the initial outline of the figure on the Prado version are corrected in free hand and it is possible to see subtle, drawn lines made in black chalk and brush that have no relationship with the painted forms. As such, they reflect the painter’s experiments and hesitations and suggest a much more complex creative process than that of a normal copy (see fig.12 - fig.13 - fig.14).
The most important point, however, is that each of the corrections to the underlying drawing on the original are also to be found on the Prado version: (see fig.15a - fig.15b) the transformation of the outline of the waist, which, as in the original, is covered by drapery on the surface; the position of the fingers (see fig.16), the outline of the veil (see fig.17) and of the head (see fig.18), even lesser modifications to the outlines of the cheeks and neck. A “traditional” copyist transcribes what is seen on the surface but not what is hidden, and the existence of these shared modifications beneath the paint surface reveals that the artist who painted the Prado panel saw the entire process of the conception and execution of the Mona Lisa. In addition, he drew elements that Leonardo drew on the under-layers but did not include on the surface, including the right arm of the chair and some internal parts of the dress (ver fig.19).