Two decades after recognising that art restoration “discoveries” and “revelations” had become very big business, we encounter a blockbuster exhibition that required a Government indemnity of £1.5 billion and was specifically launched as a vehicle to celebrate a restoration that had yet to take place: “We started thinking about this five years ago, when we were beginning to plan the restoration of ‘The Virgin of the Rocks’, so an exhibition to celebrate that project seemed like the right thing to do.” So said Luke Syson, the curator of the National Gallery’s “Leonardo da Vinci: Painter of the Court of Milan” exhibition, in a BBC interview.

Museum restorations never take place in vacuums. If you build an exhibition on the proposed restoration of a very famous artist’s work you set certain narrative expectations in motion; create pressures and hopes of big, dramatic results. When the “Virgin of the Rocks” was put back on display after its restoration – and pronounced an entirely autograph Leonardo, even though the restorer had not removed all of his predecessor’s varnish – I was pleased to discuss the then forthcoming Leonardo exhibition with Luke Syson who said that its scholarly focus would be an analysis of the influence that a new type of Leonardo painting had had on his followers. Namely, that during the 15 or so years long gestation of the National Gallery’s version of the “Virgin of the Rocks” which was delivered unfinished in 1508, and the contemporaneous (1492-98) “Last Supper” in Milan, Leonardo’s painting style had become distinctly abstracted, less naturalistic and more metaphysical in character. When I expressed scepticism that this thesis might rest secure on two such different works as the “Virgin of the Rocks”, with its uncertain condition and status (the Gallery admits the picture is “manifestly uneven in finish and execution” and that there has been “a good deal of agreement that Leonardo himself painted little or none of it”), and the degraded, fragmented, many-times restored “Last Supper”, Syson disclosed that the Royal Academy’s full-size copy of the latter by Giampietrino was being borrowed. At this, I asked if the Gallery’s own Giampietrino “Christ carrying his Cross” (which had recently been relegated to the reserve collection – on Syson’s instruction, I learned) would also be included in the exhibition. It would not. This was disappointing – and a lost opportunity to right an ancient wrong.

The “Christ carrying his Cross” had been discussed by Larry Keith, the Gallery’s new head of conservation who has restored the “Virgin of the Rocks”, and Ashok Roy, the Gallery’s head of science, in the Gallery’s 1996 Technical Bulletin under the title “Giampietrino, Boltraffio, and the Influence of Leonardo”. This followed the restoration of two Giampietrinos (his “Christ” and his “Salome”) and Boltraffio’s “Virgin and Child”. A remarkable technical discovery had been made on “Christ carrying his Cross” the ramifications of which seemed not fully to have been appreciated. Keith and Roy did acknowledge that Giampietrino’s Leonardo borrowings were “not restricted to matters of composition alone, but also include other aspects of painting technique”; they granted that the “strong chiaroscuro and dark backgrounds of Giampietrino’s small format panels are clearly an attempt to emulate the more striking pictorial effects that Leonardo had introduced to Milan”; they explicitly acknowledged that Giampietrino’s painting technique was much influenced by Leonardo’s, and that this could be “seen in the sfumato and relief of the National Gallery Christ carrying his Cross” – which painting was “clearly derived from Leonardesque prototypes” and for which “A silver-point study of Christ carrying his Cross by Leonardo [was] clearly the compositional source…” And yet, despite all of this, they seemed at pains to cast Giampietrino as a pronouncedly lesser follower of Leonardo than Boltraffio.

While excluded from the forthcoming show, Giampietrino’s “Christ” has at least been liberated from the reserve collection, making it possible for the picture and its condition to be studied before visiting the Leonardo blockbuster. Not only is it as closely related to Leonardo’s imagery and methods as has been acknowledged, it is arguably the best preserved Renaissance picture in the National Gallery. Its good condition is a byproduct of what the Gallery describes as “an unusual pigmented glaze layer”. After carefully building and modelling his forms with successive layers of paint and glazes to “an illusion of relief”, Giampietrino covered the whole painting with a single “final extremely thin overall toning layer consisting of warm dark pigments and black”. This had had remarkable aesthetic and physical consequences. The layer was contemporary with the painting and, being composed of walnut oil with a little varnish, resistant to the usual varnish stripping solvents. The use of walnut oil further relates this picture to the “Virgin of the Rocks” where that oil had been used throughout.

During the picture cleaning controversies at the National Gallery after the Second World War, the possibility that just such toning overall finishes might exist on old paintings was advanced by Ernst Gombrich. In a letter to the Burlington Magazine in 1950 and in his 1960 book “Art and Illusion”, he cited a famous report by Pliny which described the overall dark veiling finishes that Apelles had applied to his paintings to wondrous effect, and asked “is it conceivable that such famous testimonies would never have induced a master of the sixteenth or seventeenth centuries to emulate Apelles and apply a darkening varnish to achieve a more subtle tonal unity?” He then reflected “I do not think it is even claimed that our ‘safe’ cleaning methods could detect such a varnish, let alone that they could preserve it.” This provoked the National Gallery’s restorer Helmut Ruhemann (who had cleaned Leonardo’s “Virgin of the Rocks” in 1948-9 to unfortunate effect – see right) into a vehement dogmatic dismissal: “there is no evidence for anything so inherently improbable as that a great old master should cover his whole picture with a ‘toning down layer’.”

That Leonardo was a learned man and a reader of Pliny is acknowledged by both Syson and Keith in the present exhibition catalogue. In his 1962 Burlington Magazine article (“Dark Varnishes: Variations on a Theme from Pliny”), Gombrich repeated what Pliny had said of Apelles:

“He used to give his pictures when finished a dark coating so thinly spread that, by reflecting, it enhanced the brilliance of the colour while, at the same time, it afforded protection from dust and dirt and was not itself visible except at close quarters. One main purpose was to prevent the brilliance of the colours from offending the eye, since it gave the impression as if the beholder were seeing them through a window of talc, so that he gave from a distance an imperceptible touch of severity to excessively rich colours.”

How could the connection between Apelles’ final “dark coating so thinly spread” and Giampietrino’s “final, extremely thin overall toning layer [with] warm dark pigments and black” have passed without comment? The cleaning controversy of the 1960s had hardly faded from memory: as recently as 1985 it had been described by a subsequent director of the National Gallery, Neil MacGregor, as “one of the most celebrated jousts” in the Burlington Magazine. In the current National Gallery Technical Bulletin, (Vol. 32) Larry Keith, Ashok Roy, Rachel Morrison and Peter Schade, say of the restoration of the “Virgin of the Rocks” that while its practical intent was “primarily aesthetic” it also served to provide an example of the gallery’s interdisciplinary approach: “Whenever possible, major restorations are intended as the hub of a wide range of research activity that sees curators, scientists and restorers working together – increasingly alongside colleagues from other institutions”. Our criticsms of the Gallery’s customary use of restorations as effective “laboratory test cases” for conducting multidisciplinary research with an input from curators are longstanding, but what makes this unusual and pronounced “non-singing” of such a very important finding all the more perplexing is the fact that this discovery may be the tip of a scholarly iceberg. Tucked in footnote 24 of the 1996 Keith/Roy account is a disclosure that such overall toning layers are “quite rare in Italian painting of the period” and that they “may be confined to Milanese technique”. Did this mean that other instances had been found at the Gallery? Or even, given the Milanese locus, that Leonardo himself might have been the instigator or a user of such applications? (Kenneth Clark had earlier attributed disparities of finish in the “Virgin of the Rocks” precisely to damaged glazes – see right.)

When Larry Keith writes in the current catalogue that Leonardo exploited oil paint in the “Virgin of the Rocks” for its “subtle transitions and distinctions within the deepest tones, all of which were carefully orchestrated within a system of unified lighting”, he might as appropriately be describing the well-preserved effects of Giampietrino’s “Christ” as those in the “Virgin of the Rocks” where, despite the picture’s acknowledged “inconsistencies” of finish, Leonardo is said to have created a “new and remarkable unified coherence…by a carefully considered manipulation of lighting, colour and tonal values”.

Whatever the merits of Giampietrino as an artist, no Renaissance work in the Gallery shows a more tightly and subtly controlled overall development of forms, tones, colours, and expressively purposive lighting, than his “Christ”. It was unjust if not perverse when Keith/Roy, gave the laurel to Boltraffio, in part as “an artist capable of a more subtle understanding of Leonardo” but also as one who had been working in Leonardo’s studio “by 1491”, as opposed to Giampietrino of whom “it is not certain how much direct contact [he] would have had with Leonardo’s actual painting methods, and it would be misleading to assume that the imitation of Leonardo’s effects required direct reproduction of his techniques.” Under what circumstances and on whose authority other than Leonardo’s, might someone have made a full sized, exactly matching, oil-painted copy of the “Last Supper”? Besides which, in the current catalogue, Minna Moore Ede, when describing Giampietrino’s copy of Leonardo’s “Last Supper” as being with its “great clarity and three-dimensionality” the most faithful and accurate record of all, discloses that Giampietrino, just like Boltraffio, is now understood to have been a live-in apprentice who joined Leonardo’s workshop in the mid 1490s.

In the Technical Bulletin Keith/Roy saw “differences of palette” between the “more highly saturated local colour” of Giampietrino’s copy of Leonardo’s “Last Supper” and a “pictorial unity produced by a tightly controlled, restricted range of tone and value” in the work itself. That reading has been dropped: Keith now sees (Leonardo exhibition catalogue entry, p. 70) that the “Last Supper” was, as Giampietrino’s copy had testified, executed in a “higher-keyed, lighter palette” than that of the London “Virgin of the Rocks”.

Even if Giampietrino’s work had been “essentially imitative, showing more of an attempted simulation of the painted appearance of Leonardo’s works than an understanding of his ideas”, as opposed to Boltraffio’s “more sophisticated” grasp, it might for that very reason leave him the more reliable guide to the original appearances of Leonardo’s paintings than Boltraffio in his more ambitious attempts to think and compose in the manner of his master and superior. In their 1996 account, Keith and Roy undermine their own slur that Giampietrino’s overall toning layer attempted a spurious impression of a Leonardesque suppressed colourism by explaining how, in his “Christ”, Giampietrino had covered his white gesso ground with “a stiffly brushed, rather opaque imprimiture of a light brownish grey”, while for his “deep red” draperies he had first applied “an unusual strongly coloured dense red-brown underpaint consisting of vermilion, red earth and black, with an increased proportion of black used under the shadow of the folds.” Those passages of painting were further reinforced with “dark red glazes”. Taken together, it was precisely admitted that (- and quite remarkably Apelles-like), “The overall effect is restrained in spite of the intensity of colour and creates a more naturalistic effect.”

The late-discovered existence of Giampietrino’s dark toning layer constituted a repudiation of the Gallery’s former head of science, Joyce Plesters, who (in the Burlington Magazine in 1962 – “Dark Varnishes – Some Further Comments”) had parodied the very idea as a “crude device of indiscriminately deadening all the colours by the application of an overall yellow, brown, or blackish varnish”. In 1996 Plesters was then still alive (as was a long-serving trustee of the National Gallery, Denis Mahon, who had joined her in attacks on Gombrich in the 1962 Burlington Magazine – “Miscellanea for the Cleaning Controversy” ). In 1996 I asked Gombrich if the Gallery had informed him of its discovery of an overall toning layer of “warm dark pigments and black in a medium essentially of walnut oil, with a little resin”. He said not but that he was pleased to learn of the Gallery’s “final conversion to an obvious truth”. We published our first account of this episode thirteen years ago (“The Unvarnished Truth”, Art Review, November 1998). Could it be that a continuing institutional desire to spare the posthumous blushes of departed Gallery players who bungled in spectacular fashion is permanently to blight an interesting artist’s reputation, retard the gallery’s own (in many respects admirable and generously shared) scholarship and thwart full recognition of the achievements of one of the most distinguished art historians to have made home in this country?

Michael Daley

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