by Michel FAVRE-FELIX and Paul PFISTER (translation by Alison CLARKE) - updated 07/12/2015
The pictorial role of old varnishes
Oil painting differs from all other artistic techniques because the pigments
As well as its role in saturation, in this article we will discuss several additional pictorial qualities of varnish that are rarely touched upon. We will tackle the fundamental question of the ageing of varnish, and examine the multiple roles played by old varnishes in the correct perception of a painting.
Above all, it will be emphasised that the yellow colour of varnish helps to restore
We will then discuss the important role that the thickness of varnish plays in transforming the material substance of a painting into an evocative image as intended by the artist.
If a varnish has been part of the design of an oil painting from the very beginning,
Over the past twenty or thirty years, the fundamental misunderstanding of oil painting has led to mistakes that cannot be considered accidental, isolated or superficial.
When preparing to study paintings hanging together, whether in a museum or temporary exhibition, it is first of all fundamental to consider the light by which they are being displayed.
Previously, paintings had always been exhibited ideally with the light coming from the side of, or sometimes behind, the spectator.
In fact, concentrated lighting from the side reveals the rich transparencies of an oil painting; conversely, overhead lighting results in a bright, diffuse haze that interferes with the transmission of the picture to the eye of the viewer. This phenomenon can be observed, and its effects slightly mitigated, by putting up a hand to shade the eyes: the tones appear with greater precision, with the darker hues and coloured shades easier to pick out.
Yellow varnishes and the effect of depth
Entering via the Lefuel Staircase (Richelieu Wing, 2nd floor), we find ourselves in
This lack of depth should not be attributed to the fact that it is a contemporary copy. Its faithfulness to the original, now in the Hermitage Museum, is obvious, while copies of this kind were made using the same pictorial methods as those adopted by the original artist. The effect of space was obviously well understood, with the result that it can be difficult to distinguish between these old copies and the originals. The flattening, which is a common effect, should instead be ascribed to the removal of an old varnish.
We will now consider the effect produced by a yellow varnish on the sense of depth
Viewed logically, a yellow film of this kind has the effect of lessening the force of
In fact, the argument that varnish will ‘squash’ the image relies on the simplistic hypothesis that the three-dimensional effect is more marked when the contrasts
In order to establish each of these elements in the right place, properly spaced,
This would not be a problem if this adjustment lasted as it has been achieved by
This imbalance between the contrasts, which becomes apparent once the varnish is removed, acts to destroy the effect of depth as summarised below.
The greater an object’s contrast, the closer we perceive it to be. As a result, if the object’s original contrast is strengthened, it will tend to seem closer than its natural position in the painting. Similarly, if the contrast between an object and its background is heightened, it also seems to move further forward.
In addition, areas that have become murky black or lacklustre white tend to float like the jumbled pieces of a jigsaw, lacking any connection with the layered space of the painting. As these areas begin to float, and the figurative elements are forced out of their natural positions, the illusion of space disappears and our eyes register only the flatness of the canvas.
In The Fish Market, the strong contrast between the objects pushes them all into the foreground. We perceive the fishmonger’s face or the small fish at the back of the stall as being just as close as the seal, crab or fish on the floor in the foreground. If the yellow varnish were to be removed from The Game Stall, it is easy to see how the shaded areas would be transformed into black expanses. The stallholder would suddenly be pushed forward, seeming closer to us than the monkeys in the foreground.
The ageing of the varnish therefore plays a major role: it compensates for this dispersion and restores the value balance. Its yellow tint not only has a clear effect on the extremes of the painting, by toning down the strength of the blacks and whites, but also maintains the relative layering of the intermediate values. For excessively black or white areas, the varnish therefore works as a bridge, drawing these areas into the interior of the figurative space by once again linking them to the surrounding tones.
Eugène Delacroix noted the same effect of removing the varnish from old masters, and the bridging power of yellow varnish: "[…] paintings [with the varnish removed] seem somewhat metallic and monotone due to the uniformly dark appearance of the shaded areas […] The varnish’s yellow coloration, which develops over time and also affects the light areas, acts as a sort of bond between these lights and darks" (Letter to Dutilleux, 8th August 1858).
The restorer Sarah Walden has also described this phenomenon, giving the example of a painting undergoing cleaning. Initially covered in layers of browned varnish, the image is buried and lacks depth. Once the varnish is thinned, although still yellow, the three dimensions suddenly spring back to life. If the restorer carries on cleaning, however, hoping to enhance the depth still further, the opposite effect occurs and the image flattens once more (The Ravished Image, Weidenfeld and Nicolson, 1985, p. 137).
The sense of depth is one of the key facets—a fundamental characteristic—of paintings in oil and varnish. How can restorers fail to see how space is destroyed by the removal of varnish? How can they misconstrue the pictorial technique to the extent of destroying an artistic triumph? Is it the fault of the modern world that we no longer understand the ‘naïve’ illusion that these great artists strove towards in their art?
In room 38 (Richelieu Wing, 2nd floor), The Ray of Sunlight by Jacob van Ruisdael should act as a fabulous demonstration of the evocation of space and atmosphere. The composition of this huge, theatrical scene, lit by shafts of sunlight, leaves the viewer in no doubt as to the effect originally intended by the artist. However, the loss of the original varnish (and certainly also its glazing) leaves the painting feeling monotone and with a somewhat lunar light—in stark contrast to the painter’s conception.
Restoration requires points of reference: it is important that these are found in the best-preserved works, and not just in paintings from the restorer’s own museum collection.
In cases of over-cleaned paintings, an alternative solution can be to add a layer of lightly tinted varnish (as reversible as the other retouches and duly reported in the painting’s conservation file). This method, recommended by Paul Pfister, is already in use in various museums but, to date, the Louvre has refused to countenance it. In other instances, a traditional varnish can be applied thickly enough so that its ageing should be perceptible within several decades.
The confusion of relative contrasts, which is heightened by the lack of an old varnish, not only impairs the rendering of space but also has a further consequence. The painter will not have concentrated solely on ensuring that the figures and objects in the painting are correctly positioned in the image’s fictional space. In addition, he will also have ensured that these various elements are ranked in their ‘order of appearance’ upon the scene.
The fact that viewing is not an instantaneous act is normally completely ignored when it comes to the perception of paintings. While painting itself is a static art, the reception of a painting has to take place in real time: neither eyes nor brain are capable of absorbing all of the components of a work all at once. This is, in practice, not a problem. Indeed,
When we look at a well-preserved painting, we share this experience. The artist initially offers us a first impression of the painting’s main forms, striking groupings, foremost figures and key colour arrangements. However, he has also built in paths to other aspects that are not so obvious at first glance. Little by little, we begin to pick out more complex relationships such as colour tones that we had previously overlooked, or figures or objects emerging into our awareness. The whole painting begins to come together to form an entire world.
Where the state of the painting still permits it, this experience of progressive revelation goes hand in hand with our equally progressive immersion in its depth of space. This is not a coincidence: the two effects of depth and temporal discovery are both woven into the carefully adjusted contrasts throughout the painting. For this reason, the inconsistencies that appear when the old varnish is missing also affect the viewer’s temporal journey. We have often noticed this: it is hard to know where to look first when faced with a confused assortment of objects, all fighting for our attention. It seems impossible either to begin looking, or to continue to do so. Our gaze is assaulted by the minutiae of details, the 'readability' of which the restorer may have endeavoured to enhance but which in fact ensure that all of the elements of the painting are presented to us at once. The secondary elements no longer function as enhancements, as the painter had intended, but instead add their voices into a cacophony.
Our observations thus far can be summarised as follows: an old painting and an old varnish form a coherent unit or system where the various ageing processes balance and compensate for each other. Is this really so surprising? Should we not, instead, suspect that something has gone awry when faced with an old master that has been sprayed with a colourless, synthetic varnish?
Varnish thickness, transparency and the coating of brushstrokes
The purpose of varnish is not just to establish depth from the very beginning, and later to ‘restore’ this effect of depth by yellowing and compensating for the growing discordance of values over time. In addition, the thickness of the varnish allows it
Transparency and the coating of brushstrokes
By coating the brushstrokes, the thickness of traditional varnishes gives a sense of elegance to the painting and envelops its materials in mystery. In this way, painters aimed to smooth their workaday brushstrokes close to invisibility. An illuminating comparison can be made between two Vigée Le Brun portraits in room 52 (Sully Wing, 2nd floor).
In her portrait (fig. 4), which had its varnish carefully thinned a long time ago,
The painting of Madame Molé-Raymond (fig. 5), meanwhile, was completely stripped of its varnish (‘heavily thinned’) in 1994. It now features only a thin, colourless finish, which no longer conveys any sense of the subject’s skin. Instead, it resembles a palette daubed with brushstrokes: the marks of the paintbrush, such as the streaks on her cheeks, stand out vividly, and everywhere the eye is assaulted by accumulations of paint. The picture seems to have been painted in acrylic rather than oils, despite the fact that these two paintings by the same artist are both on wooden panels and feature the same artistic techniques. It is simply that the old varnish is missing from one painting and not the other.
It is a mistake to believe that, because of his habitual use of vigorous brushstrokes, Frans Hals would have wanted these marks to have been rendered quite as obvious as cleaning is doing today. Hals varnished his paintings and the evidence points to the use of a very substantial oil varnish. The audacious style
It is worth celebrating the fact that such a significant number of the Louvre’s Dutch paintings still feature this style thanks to the efforts of Jacques Foucart, their conservator until 2005. Further examples include the Rembrandts (from Bathsheba  to the Carcass of Beef) and Van Dyck’s portrait of Charles I, which display the effects of the varnish thinning, carried out in the 1950s. Particularly laudable is the care taken to preserve the beautiful appearance of a rare female nude by Van Dyck, Venus at the Forge of Vulcan (room 26, Richelieu Wing, 2nd floor).
A subtle boundary
This problem merits further discussion: paintings that have been completely stripped of their varnish and then covered again with a thin, colourless layer convey an overt sense of materiality. The physical painting — a flat canvas covered with paint — takes precedence over the palpable representation of figures and space. Cesare Brandi called this ‘the material babble’, which acts to shout down the image’s mysterious presence or ‘epiphany’.
When seeking to explain this phenomenon, it is worth reiterating that the coloured layer ‘discovered’ during deep cleaning is very far from having remained intact.
However, this original exudate rarely survives the repeated application of solvents.
A rare example of a painting that has retained the majority of its original structure is Poussin’s 1657/58 Santa Francesca Romana (room 14, Richelieu Wing, 2nd floor) (fig. 6). From what we know of the painting’s history, it appears that it was not completely stripped of its varnish until it was cleaned in 1999, when the varnishes were removed but the top skin of the painting was not entirely eliminated .
The delicacy of the painting’s colours, such as the reddish glazes that still tint the angel’s green robes, or the soft blue of the drapery of the prone figure, should be compared with the current colours of Poussin’s other works in the same room. The crudity of these later paintings is a symptom of the flayed surfaces on which the colours stand out vividly and incongruously.
The evolution of French museums
Although in theory French museums are committed to the doctrine of varnish thinning as formulated in the 1950s, over the years they have leaned towards the practice of removal known as ‘advanced thinning’. Proof of this is provided by Domenichino’s
The cleanings at the Louvre over the last two decades were not carried out for reasons of preservation, as the paintings were in no danger. Instead, they were carried out for aesthetic purposes. One might therefore expect some level of aesthetic justification, whether in terms of the creation of the work (what materials were used?) or in terms of the artist’s expression (what effect was intended?). However, instead of such arguments, the only motivations to be found in the dossiers are to get rid of the yellow tone of an old varnish (termed ‘oxidised’) and, therefore, to achieve ‘readability’ for paintings.
The illusion of readability
‘Readability’ is a deceptive notion, as a picture is not designed to be read .
Nevertheless, if the word is to be understood in a certain sense — as ‘highlighting artistic expression’, for example — it is important to note that paintings restored in this fashion have not been made more ‘readable’, but in fact less so.
For example, in Herds in a Hilly Landscape by Cornelis Huysmans (Lefuel Staircase), all of the vegetation has darkened over time. The sky has remained light, and has doubtless been over-cleaned. The removal of the varnish has not revealed any additional elements; it has done nothing but exaggerate the brutal disconnect between two overly contrasting areas.
Canvases prepared with red-brown grounds pose even more frequent problems.
With the varnish gone, the painting simply appears to be made up of dark, monotone areas, from which emerge disassociated elements in colours that have often been attacked by solvent leaching.
In the examples that we have seen, the removal of the old varnishes simply makes the artist’s original message unreadable. The gradual discovery intended by the painter becomes a confused tangle, with any perception of depth reduced to a sensation of flatness. Instead of bringing readability to the tangible interpretation of subjects such as the fresh skin of the sitter, cleaning instead forces us to ‘read’ brushstrokes and paint marks.
The obsession with yellowing
The current ideas on restoration can be boiled down to an obsessive struggle against
Even a certain level of yellowing has now come to be perceived as an unacceptable fault, although this had previously been seen, with reference to the pioneering cleaning doctrine developed by René Huyghe at the Louvre in the 1950s, as attractive and important for the perception of the work. For example, Huyghe warned against the deep cleaning of the seventeenth-century paintings, arguing that "the blues of Poussin, Claude, Le Sueur and others have become somewhat aggressively glaring over time and so stand out from the other colours, upsetting their original balance".
The Louvre’s seventeenth-century French paintings demonstrate the wholesale abandonment of these principles. Notable is the series of 21 paintings in the St Bruno cycle, painted by Le Sueur between 1645 and 1648 and stripped of their varnish between 1981 and 1993 (room 24, Sully Wing, 2nd floor).
The large altarpieces in room 29 (Sully Wing, 2nd floor) have undergone such serious thinning of their varnish, both recently and long ago, that these oil paintings now look more like frescoes. Examples include Laurent de La Hyre’s Christ Appearing to the Three Marys and Noël Coypel’s St James the Elder. This is an aberration because, although the seventeenth century valued clarity in artistic expression, painters could not or did not want to surpass the methods inherent in the oils technique.
In some cases, paintings that have been weakened by the application of solvents become porous. In Sébastien Bourdon’s
This obsession with yellowing equally applies to revarnishing, where a sprayer is used to apply an ultra-thin layer of synthetic resins. In this field, as with cleaning, the cautious reputation enjoyed by French museums is no longer at all justified: for some time now, the use of acrylic resins and particularly ketones (polycyclohexanones) has been widespread. The presence of these chemicals is fairly easy to detect on several canvases in the Louvre — including Poussin’s masterpieces Spring, Summer and Autumn — due to their lifeless, plastic appearance.
Because the molecules in these resins are too large, they cannot be used to achieve the correct saturation of colours. These were at first championed as they would not yellow and would be easy to remove. Actually, they might become even more difficult to remove than natural mastic varnishes, sometimes requiring the use of strong, penetrating solvents.
The most egregious example of modern times is the Van Eyck brothers’ masterwork known as the Ghent Altarpiece. This is in urgent need of restoration, currently ongoing, to remove the synthetic varnish applied in 1950's and later to the panels of this treasure of world heritage. These ketone resins are now threatening the painting, and get harder and harder to dissolve the older they become.
A note on colour perception
We still need to consider the main accusation constantly levelled against the yellow tone of varnish: that it denatures the cool colours and, in particular, turns blues green. This prejudice withers in the face of evidence, however, as can be seen from paintings such as Vouet’s Polyhymnia, Muse of Eloquence (Fig.7) (room 30, Sully Wing, 2nd floor). Here, the even blond varnish acts as no impediment to the full enjoyment of the picture’s coloured tones, which range from ultramarine to pinks, ochres and off-white.
The same experience holds true in front of Chardin’s masterpieces The Attributes of Civilian Music and The Attributes of Military Music (Fig. 8) (room 49, Sully Wing, 2nd floor). These two paintings are associated with a famous remark by Diderot, who, on coming to admire the newly finished works at the Salon of 1767, warned visitors not to be disconcerted by the "somewhat raw and harsh glare of the fresh colours" that would be "extinguished" by time. He advised the viewer to "revisit these works once Time has painted them". When the two paintings entered the Louvre from a private collection, their varnish had been preserved in an even, transparent state without additional thinning. Its golden tone helps to highlight all of the subtle differences between the coloured tones: the blue has not turned green, while the pinks, reds, brownish reds, vermillion and carmine have all kept their hues without any confusion.
A colour measurement instrument would obviously reveal the presence of yellowing,
Authenticity, original and historical varnishes
Now that this journey is complete, we can suggest a general course of action:
For all paintings that were originally designed with a varnish but have lost their original coating, an old varnish, featuring natural resins and the attendant yellowing, should be considered authentic and should be preserved.
The public believe that museums study the materials used by artists and endeavour to reconstruct the type of finish that would have originally been chosen. This is not the case. How would the public react if they were to be told that restoration instead strives to impose a modern, industrial finish upon old paintings?
As for the study of varnishes used by artists in the past, this has long been ignored by museums and labelled useless or hypothetical. However, this position can no longer be justified: in addition to the wide range of knowledge already available from historical sources such as recipes or written testimonies, new types of scientific analysis are now revealing the composition and characteristics of varnishes, such as the resins they contain.
In the case of Orazio Gentileschi (1562-1639), several years ago at the Getty Museum an original varnish was identified on his Lot and his daughters executed in around 1622. It consisted of colophony (or rosin, resin extracted from the pine) and Manila copal (sometimes bracketed with other closely related resins under the general term ‘amber’) . This final, golden layer also corresponds to the warm coloured "amber varnish from Venice" that Turquet de Mayerne, a contemporary of Gentileschi, describes him using [see Nuances 36-37 : Les vernis originaux dans la peinture italienne -14eme-17eme ].
Given this crucial technical information, what can we deduce about the two Gentileschi paintings owned by the Louvre, which were painted between 1624 and 1628 and are currently on display in the Grande Galerie?
The Rest on the Flight to Egypt (fig. 9) still features a faintly golden natural varnish. Although unlikely to be original, this varnish is very similar to the original coating identified by the Getty. Its presence is therefore fully justified because of the aesthetic authenticity that it brings to the work, and specific arguments in technical art history support its conservation.
In contrast, extremely powerful solvents were used to strip the varnish from Gentileschi’s other painting, Public Happiness Triumphs over Danger, in 1978. The work was then sprayed with a synthetic varnish. Neither historical nor aesthetic justifications can be found to defend this treatment, or its appalling results. Nevertheless, this type of systematic, ungrounded ‘restoration’ has been imposed on almost all of the Italian paintings of this period, including those by Guercino, Guido Reni, Pietro da Cortona, Albano, Carracci — who share, along with Gentileschi, the characteristics of Counter-Reformation art — and of others Italian painters of the fifteenth and sixteenth centuries, in spite of their various aesthetic conception.
The study of original varnishes, thanks to newly discovered analysis techniques, is just getting off the ground. The discovery of many of these original varnishes, even just as traces, still in situ on old master painters has already — finally — supplied incontrovertible evidence that calls into question museum practice and the received ideas of modern restoration.
To contemporary tastes used to bright,
Likewise, it is very likely that Rembrandt used a mastic resin varnish — possibly mixed with a resinous balsam, Venitian turpentine — this can be used as a reference point for judging the conservation of such paintings .
All the same, not all old varnishes are in a satisfactory condition, and treatment is required for their preservation. A lack of transparency is notable on the lower half of The Plague at Jaffa by Gros, for example. A greyish haze is also present on Georges de La Tour’s St Sebastian Tended by St Irene.
The true aim of a conservation project should be to bring transparency to a varnish, and to treat it without resorting to removal. There are solutions that keep this aim firmly in mind — as opposed to the unjustified cleaning programmes put into practice to date.
Michel Favre-Félix and Paul Pfister
Translated by Alison Clarke
for the translation © Alison Clarke
 In terms of blue alone, smalt can either remain cobalt blue or transform into greyish-brown; lapis lazuli can either whiten or maintain its dark blue radiance; and azurite has a general tendency to darken.
 Either due to the discolouration of their pigment, or because the bright sections have often been excessively scoured duringold cleanings that have wiped away the painter’s careful graduations in tone.
 Since we first published this study in French (2007), the Louvre has planned a restoration of Rembrandt’s Bathsheba. At the very beginning of the cleaning tests (March 2014) we have been given the chance by the Head of the painting department, during a meeting attended by the curators, the restorer and a member of the C2RMF, to present our arguments defending the pictorial role of the old varnish still present on this painting and the aesthetic adverse consequences that might come from any pronounced cleaning.
Eventually, the Louvre’s intervention was restricted to the lightest surface cleaning, preserving - in our opinion - both the overall unity of the painting and the sensitive perception of this outstanding nude. The result can be appreciated on the Bathsheba, back in the museum’s room since June 2015.
 The haste of the 1999 restoration must still be condemned, however, as there is every reason to believe that the original varnish was still in place. It was removed before the results of the analyses showed — too late — evidence of ingredients typically in use in Poussin’s era (mastic resin, colophony and sandarac).
 On the French term lisibilité — which should be translated as ‘readability’, rather than simply ‘legibility’, in order to encompass the additional dimension of ‘comprehension’ — see Michel Favre-Félix, ‘Ambiguïtés, erreurs et conséquences : Rendre l’œuvre lisible’, Revue CeROArt [Conservation, exhibition, Restoration of works of Art.], 3-2009. URL: http://ceroart.revues.org/1140 . See also Salvador Muñoz Viñas, Contemporary Theory of Conservation, pp. 99-101, Elsevier Butterworth-Heinemann, 2005.
 see Mark Leonard, Narayan Khandekar and Dawson W.Carr,'Amber varnish' and Orazio Gentileshi's 'Lot and his daughters', in The Burlington Magazine, Vol CXLIII, number 1174, January 2001, pp. 4-10.
 For the traces found on Carravagio’s works, see Roberta Roani, in Riflessioni sulle “Regole per comprare, collocare e conservare le pitture” di Guilio Mancini, p. 31, Edifir Edizioni, Firenze, 2005.
 Samuel Dirksz van Hoogstraten, who was one of Rembrandt’s pupils, notes in his book Inleyding tot de Hooge Schoole der Schilderkonst (Introduction to the Academy of Painting — Rotterdam 1678) on the varnish in current use in his circle: “Our varnish, consisting of turpentine [balsam from pinaceae, usually Venitian turpentine], spirit of turpentine, and pulverised mastic dissolved, is sufficiently convenient for our works” (Inleyding …, p.223). It would have been even more coloured than pure mastic, given the original orange hue of the Venitian turpentine, which both increase over time.