In 1997, the process of cleaning and restoring the painting was undertaken.
The first cleaning surprisingly revealed, after eliminating the thick yellow varnish and heavy retouching, that the original brushwork was of excellent quality.
Chemical analysis showed that the micro-fragments taken from the mantles of the Virgin and the angel and from the background rocks are pigments used in the Cinquecento – specifically, the blue is made with azurite, which hasn’t been used by painters since the 19th century. There can be no doubt regarding the dating of the work.
Scientific examination confirms that the linen canvas is also from the Cinquecento.
It is tightly and regularly woven, and quite thick, without any stitching. Prior to the early 19th century, it was relined.
During this early intervention, the paint film was certainly subjected to an overzealous cleaning, which heavily abraded the upper, more delicate layers – i.e. the glazes that softened the contrasts between light and shadow with Leonardo’s famous ‘sfumatura’, while also emphasizing the fine details of the figures and landscape through ‘aerial perspective’.
In his ample retouchings, the early restorer-painter had enlarged the eyes of the figures, added curls to their hair, fringe to their garments, and inserted an architectural complex into the landscape, having probably erased the original.
It was therefore decided to remove the retouchings, which in fact revealed the good condition of the underlying paint film, with few and minor losses of the original colors.
These two investigative methods rendered visible only a few suggestions of a preparatory drawing and no corrections (understandably, as this is a copy of an existing work).
The imprimitura – the thin colored layer on which the painter was built – has a gray tone resulting from a mixture of lead white and particles of plant-based carbon black.
The luxurious mantle of the angel, for example, has a light red lower layer containing red ochre particles, and an upper layer with fine Garanza lake pigment, both with an oily binder. The red lake is very brilliant in hue with a gossamer glaze; the Virgin’s mantle, on the other hand, has an underlying brown layer, over which is applied a dark blue made from precious azurite.
The flesh tones of St. John are instead composed of lead white, red ochre and vegetable black with a mixed binder of egg and oil, Leonardo’s notorious “tempera grassa”.
This scientific analysis reveals surprising technical peculiarities: the use of canvas supports in the early 16th century was very rare, and in fact the works of Leonardo da Vinci and the Lombard painters close to him are all on wood.
The priming layer of the Borghetto Virgin is different from those most commonly used during the Sforza era in Milan, where a light orange-pink tone prevails. It should be noted, however, that the grayish ground is shared by the London panel.
There are also certain eccentricities in the choice of pigments: in Lombardy, for the base layer of the red lake glaze, painters did not use red ochre, but cinnabar (the blue of the Virgin’s mantle in the London version contains, in addition to azurite, the highly prized ultramarine blue made from lapis lazuli).
In our painting, the compositional variety of each color is truly extraordinary: each fine layer binds the pigments with a medium created by mixing different binders using a scientific technique developed by Leonardo in which egg, certain oils, and glues are expertly deployed to create a specific chromatic result that impacts both the tone and the luminosity of the painting.