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Moving pastels – again

4 November 2018

Readers of this blog will be aware of my scepticism about the safety of moving pastels, and it is encouraging that the debate is taking place more widely. Less encouraging however is the fact that many important pastels continue to travel to loan exhibitions before any consensus has yet emerged. So I make no apology for reverting to the topic, and attach a talk I gave in April to a round-table of professionals held in London. I didn’t post it at the time because I expected a broader statement to emerge centrally, but the issues deserve wider discussion and urgency.

There was a range of different views which I am not going to attempt to summarise. Suffice it to say that some of us disagreed with the idea that there are safe means of moving pastels, or that conservators should agree to unnecessary movement just because there are pressures within their institutions to sanction it. Damage to pastels is a phenomenon recorded over 300 years, and despite every type of handling, cushioning and transport having been investigated over this period, there is no consensus on what minimises, let alone avoids, damage. The mechanisms appear to be subtle but cumulative, making it all the harder to establish any safe harbour.

If you are really interested I recommend you read the more focused discussion in chapter V of my Prolegomena: it is freely available online as a pdf, and has the detailed references you won’t find in a lecture. It also sets out more clearly than I do in the lecture the real barrier to progress in this field: the absence of research into the nature of the bonding mechanisms that hold pastel in place. No real progress will be made until fundamental research is undertaken into bonding – a multi-disciplinary project looking at mechanical, chemical and electrostatic effects at a microscopic level. That research has yet to be done.

Here then is the text of my talk given in April.


We are all here because we want pastels to be better known, and we recognise that loan exhibitions would help with that common objective. But then we divide – not into two, but like Gaul, into three camps: the Enthusiasts, who don’t believe there’s any special problem moving pastels; the Compromisers, who think that the scientific value justifies taking a calculated risk; and the Neinsager, or Naysayers, who think we don’t yet have an effective protocol and so shouldn’t move them unless absolutely necessary. In the 30 years I’ve been interested in pastels I’ve moved from the first, to the second and then to the third camp, where I’ve been since 2004 for reasons I’ll come to later. Incidentally I continue to lend work in other media to travelling exhibitions as I have done since 1981, and I would love to return to the first camp.

I gave a longer talk at the Petit Palais in Paris last October with a fairly complete taxonomy of the risks to pastel. I’ll try not to repeat too much of it. You can also find references in the document called Prolegomena on my website.

But today I do want to ask: how is it that these camps can disagree so fundamentally? Can the differences be explained solely in terms of personality types? Is it pastels which are abnormally sensitive, or just their owners? Or is there a real issue?

As we all know from the third paragraph of Chaperon’s famous treatise, pastel is precarious. It is simply dust rubbed into paper. Not even the binder used in making the crayons is supposed to contribute to adhesion (although personally I’m not entirely convinced of that – the fact is we simply don’t understand the complexities of bonding in pastels). The wonder is not how easily pastels are damaged, but how any pastel survives.

I don’t need to remind anyone here that the official policy of most museums is not to lend, so let us remember that the onus of proof is on the Enthusiasts to demonstrate that moving pastels can be done safely.

No one is suggesting that moving art of any kind is entirely without risk. Other media can also be vulnerable:


This text has got nothing to do with pastels, but when Bernini asked this English traveller about his bust of Charles I which he had sent to London, he was more interested in whether it had survived the journey than in whether its likeness had been praised: “I tooke as much care for the packing as studye in making of itt”. Bernini’s concern brings home to us the moral right of artists not to have their work damaged carelessly.

Now a sculpture either breaks or doesn’t. (A flaw in the marble will probably reveal itself before the sculptor has finished.) But the Neinsager believe that damage to pastels is not binary. The fundamental difference is the possibility of invisible damage.

The Enthusiasts probably share this rather reductionist thinking:


In other words, if you can’t see dust lying on the spacer at the bottom, the picture hasn’t been damaged. What you see is what you get. There’s simply a shock level above which pastel falls, below which nothing has happened.

For the opposite view we need to look at this (conceptual) pigment degradation chart:


When a pastel is made, the last thing the artist does before framing is to give it a tap to release any loose dust. That’s the first stage. The next is the loss of the very delicate “fleur” which I suspect has largely vanished from most 18th century pastels. Now the Enthusiasts think that’s it – barring a catastrophe, no further particles will fall. But the Neinsager identify two further phases, and these are I think at the heart of the disagreement. If you accept either possibility, all the evidence from safely transported pastels becomes irrelevant to our debate.

First there is the concept of latent damage which is completely invisible. I will leave Leila Sauvage to discuss how adhesion may fail after a build-up over time analogous to metal fatigue in aviation engineering. The medical analogy is not so much haemophilia, but brain damage in boxers who appear fit after each fight.

But secondly there is the possibility of damage which appears as a subtle change in luminosity but which doesn’t result in any noticeable displacement of particles. If you haven’t seen this for yourself, you probably won’t believe me. But my Damascene conversion was 14 years ago, when I observed two pastels which travelled to different exhibitions in France. One came back in perfect condition; the other looked fine on immediate inspection and comparison with the Ektachrome taken before it left, but then I began to notice that something wasn’t quite right. Put simply it had become dull. There’s no slide because you can’t see any difference in the photographs – all the particles seem to be in the same place.


But my suggestion is that what may have happened is not complete debonding, but minute realignment. This is happening somewhere between the molecular scale, where the forces that hold crystals together would snap them back into line, and the larger particulate scale, where debonding would lead to falling. In other words the search for failure, through fatigue or otherwise, is focused on the wrong issue: the true enemy is not gravity, but entropy. Instead of the pigment escaping to the bottom of the frame, like the Scarlet Pimpernel, those “demn’d elusive” particles are hiding in full sight.

But we do need to put this connoisseurial assessment onto a scientific basis – perhaps it is visible at ultrahigh magnification, but that type of investigation hasn’t been done, and can’t be done after the fact. At present, you can’t prove the damage, and you can’t make an insurance claim. And anyway insurance policies usually exclude pastels as having what is called inherent vice.

Of course pastels are also exposed to the same insurable hazards as other pictures, including theft


as well as minor damage from chipped frames, broken glass and so on. But the second component of the debate is that for pastels, these have different consequences. Every time a pastel comes out of its frame there are vastly greater risks than with an oil painting. Consequential damage ranges from the danger of touching the surface or cutting the support when you open it to what can happen from the air-borne gesso that pervades the gilder’s workshop when you take it in to be reframed.


Unlike oil paintings which everyone knows have been restored repeatedly, for many of us the great delight of pastels is that they can and should be in their original condition. Pastel damage can’t be mended using reversible techniques – although it’s fair to say that a far larger number of pastels have sadly been “restored” than is commonly realised.

The Enthusiasts’ best argument is how difficult it is to identify specific pastels that have actually been damaged by transport. It is indeed very rare that you find reports like this about Russell’s Moon now in the Oxford Science Museum:


There is quite a lot of evidence in Rosalba’s correspondence, but mostly you can’t identify the pastels concerned – if indeed they survived at all. “Survivor bias” is just one of the cognitive errors surrounding the detection and reporting of damage which I discussed in detail in Paris. Indeed there’s a special version of it for those of you who work in museums, and are never exposed to the wrecks that auction houses regularly show me.

The problem has of course been known for a very long time. Here’s the inscription on the back of this 1670 Nanteuil pastel sent to the Uffizi: “don’t handle this picture roughly”. Or the inscription on the reverse of Liotard’s pastel of Lord Albemarle: “aucun coup de Marteau”; nevertheless something has happened to the red coat, more than just light fading.


Or this touching letter from Oudry to his friend comte Tessin sending a pastel to Stockholm as a gift: “transport always displaces pastel onto the inside of the glass and spoils the work”:


And when this account was published in 1742, the notion that pastel was “périssable” was already a trope. Even the poetry of the day accepted that pastel was a metaphor for fragility, as the cardinal de Bernis implied: “à force de venir, revenir, voyager/La couleur se détache & commence à changer!”, then a joking reference to Loriot, the celebrated fixer:


But of course fixing doesn’t work. The poet Ezra Pound put it more succinctly than I can: “great artists don’t like it, ’cause it bitches the colour.” The idea itself is misconceived – one author called it a “profanation”: why destroy the very thing you like about the medium?


And even where it was used 250 years ago, we don’t know if it’s still effective in any particular case. Incidentally when Loriot fixed Perronneau’s portrait of Le Normant du Coudray during a trip to Orléans, the pastel was already six years old and had been back and forth to Paris three years before. You can see that what remains isn’t in brilliant condition. It’s just a bit … dull.


If we take an important artist like Perronneau, where anything with even a partial signature is likely to be kept, we find fewer than 230 autograph pastels are known even from photographs. That is a far higher percentage than for more minor figures, but of this œuvre, on my estimation, half are in compromised condition, and a further quarter perhaps can be described as ruined.


Estimates of losses are always going to be controversial and inaccurate: for only a handful of artists do we have complete work lists. But using statistical sampling methods, it is possible to form order of magnitude estimates. I reckon that the 18,000 or so known images of pre-1800 pastels probably represent less than 3% of the professionally created works of that period. While this is a pretty rough estimate, I think this is a significantly lower survival rate than for oil painting.


The comparison of two autograph versions of the same work which have different conservation histories can provide us with fascinating information, just like medical trials on genetic twins. Here are two versions of Canova in his studio by Hamilton.


Or again Liotard’s Lord Mountstuart: the Getty version left, the other still in the family.


But how much of this is caused by transport? The Enthusiasts will tell us how often they’ve supervised pastels travelling to exhibitions which have returned safely. Incidentally they also tell us that they only allow pastels to travel after a careful selection procedure: is this I wonder to chose those that have already lost their fleur, or only those that still have something to lose? The question isn’t entirely facetious, as you can only answer it if you know the shape of the degradation curve.

The answer is not just that I don’t know, but no one does. That’s the point. The time fuse for latent damage to emerge is too long. Comparison with pre-despatch photos won’t detect subtle realignment. One pastel may be damaged taking it off the wall; another may cross the Atlantic four times without apparent damage. Dealers routinely drag stock from Paris to Maastricht, New York etc. We just don’t know what the causes of deterioration are or why they affect some pastels earlier than others.

What we do know is that today pastels are travelling further and more often than at any time before: you have to ignore the blip caused by a huge dealer’s exhibition in 1911.


And with Emmanuel Macron’s campaign of soft power in full swing, not to mention the problems for museums who can only charge for temporary shows, we can expect more – despite the fact that the money made from travelling programmes is often far less than expected. Pastels can get caught up in politics and the voices of conservators drowned. Official non-lending policies simply get ignored.

As recent reports from the Louvre in relation to the proposed tour of the Mona Lisa put it: “the vibration-free transport system has not yet been devised”. I don’t need to remind you that on her last trips, she survived an attempt to spray red paint over her in Tokyo, while at the Met in New York she was flooded with a faulty sprinkler system. A pastel would not have survived.

Water is the medium’s greatest enemy after kinetic energy. You might think it irrelevant to lending.


But when the La Tour show opened at Versailles, the vernissage was held on a very wet day. When the throng of visitors were finally admitted, humidity levels were high enough for condensation to form inside the windows.

And it’s not only in the lorry that problems can occur when you lend your pastel. Installation and deinstallation, which is often more chaotic:


lighting; maintenance – both floor polishing, and overenthusiastic glass cleaning, particularly with so-called anti-static glass: these are all hazards your pastel won’t face at home. Even if your pastel can be carried by hand, are you sure the other exhibits won’t need something a bit more powerful?


Footfall in the galleries, for example from increasingly popular gymnastics activities,


filming, loud music or even external events can cause concerns sufficient for the board of trustees at this institution to discuss the measures necessary to protect objects from them.


Only a few weeks ago as I visited the Charles I exhibition at the Royal Academy I was shocked by the level of vibration from drilling works for the link bridge connecting Burlington House with the Burlington Gardens building.


Again these problems are not new.


When Henri de Rothschild bought La Tour’s Duval de l’Epinoy, he hadn’t reckoned with the new bus route at his home, and ended up building a new house: as you might say, “ace pastel with quite a nice home attached”. Rothschild may have consulted Charles Moreau-Vauthier, whose La Peinture appeared the following year, and contained a discussion of the effect of vibration on pastels mounted on stretched canvas, noting that the resultant “tambourine…vibrated to the noise from neighbouring streets.”


Moreau-Vauthier proposed a system of double lining pastels with a second canvas, primed on one side, intended to offer destructive interference to counter resonance. My point with this story is that sophisticated solutions to the vibration problem have been suggested for more than 100 years: they just don’t work. We’ve been around these houses before.

Even with lorry transport on which so much research has been carried out as I discussed in Paris, there are concerns. There is much useful research on crates – the smaller the better, but that battle is not yet decided.


We are told of solutions involving extra layers of foam. But these miss the point: as research as shown, you can only eliminate the resonance for one frequency, and you do so at the expense of others. Redistributing kinetic energy is like herding cats. So when I’m told the problems have been solved, and the solution turns out to be … just another layer of foam, I remain unpersuaded.

Take something as basic as glass.


The protocols say: replace it with something stronger. This is slightly curious as it implies that it’s ok to subject the pastel to enough shock to break a sheet of glass, although it does show a better grasp of the consequential damage concept. Let’s not debate whether a much-vaunted make of acrylic sheeting is safe: personally I wouldn’t touch it. But what do you do when your clients don’t want to remove old glass? To have any evidential value a protocol must be consistently applied; it is useless if you abandon it on a whim. But equally, is unnecessarily changing the glass within the ICON duty to “conserve cultural heritage [as] reliable evidence of the past”? Was it not a great tragedy when the original glass for the président de Rieux, now in the Getty, was broken when the picture was dropped while still at the château de Pregny – a sheet so rare that the maker had uniquely etched his name onto it?

We try to devise work-arounds.


So we remove the glass and transport the picture attached only to its strainer. That seems an excellent idea – provided the package isn’t opened by an over-zealous customs inspector – but in fact it would be the very worst thing to do if you believe that the presence of the backing board and glass are essential to damping the vibration in the canvas, as some research shows.

So you switch your attention to the billowing canvas problem. You might put some wadding between the pastel and the backboard to absorb vibrations. But the elasticity of the quilting can potentially exacerbate the problem. And putting polyester wadding in direct contact with parchment (as I’ve seen done) creates static electricity which is worse than taping the glass. So often this can seem like a game of whack-a-mole.

The issue is not that we don’t understand the solution, it is that we don’t really have a holistic grasp of the problem. We’ve no idea what a real pigment degradation curve looks like. We don’t know at what specific frequencies vibration is a risk; we don’t even know if we’re dealing with physics, chemistry, biology or crystallography. This is a multifactorial problem. And because of the innate idiosyncrasy of each pastel, and the fact that we can’t do destructive testing on a representative sample of each class consisting of a single object, we can’t prove that solutions will be effective. Even if you relax the strictness of that logic, a proposed solution would only be credible after many years of use on hundreds of pastels. So my view is that the claims that the problems have been overcome are overambitious.


While what I’ve been saying is aimed at the Enthusiasts, I have one thing to say to the Compromisers: you can’t take calculated risks when you can’t calculate the risk.

Finally I want to talk about another barrier to solving this problem: the culture of secrecy that the art world embraces, particularly concerning damage. For all sorts of reasons damage is rarely disclosed and even more rarely documented with the high-resolution images in repeatable conditions that might give advance warning of failure. What we need is the equivalent of the universal cancer databank that’s just been launched.

This then is a programme for research:

  • Document/share – images and data on pastels, protocols and actual transport histories
  • Don’t think that you can fiddle with just one issue, and declare the problem solved
  • Figure out how pastels disintegrate before trying to figure out how to protect them
  • Figure out if the problem is physics, chemistry, biology or crystallography…
  • If you don’t have a mathematical model that can tell you what one 10g bump in an air cargo ramp equates to in road miles or number of single shocks of 1g on an air-cushioned lorry etc., you don’t know what is happening
  • Stop lending pastels until you know
  • And if you aren’t prepared to lend, should you be willing to borrow from those who may know less?
  • Finally: Remember Bernini.

From → Art history

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