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Rocking the Louvre: the Bergeon Langle Disclosures on a Leonardo da Vinci restoration

28 April 2012

ArtWatch has been haunted for two decades by a nearly-but-not-made restoration disclosure. In the 1993 Beck/Daley account of the Nippon TV sponsored Sistine Chapel restoration (Art Restoration: The Culture, the Business and the Scandal), we reported that in the late 1980s Leonetto Tintori, the restorer of Masaccio’s “Trinity” in the Santa Maria Novella, Florence, and a member of the international committee that investigated the controversial cleaning, had “urged the Sistine team privately to preserve what he termed ‘Michelangelo’s auxiliary techniques’ which in his view included oil painting as well as glue-based secco” (p. 111). What we had not been able to say was that Tintori (who died in 2000, aged 92) had prepared a dissenting minority report expressly opposing the radical and experimental cleaning method.

Shortly before the press conference called to announce the committee’s findings, Tintori was persuaded by a (now-deceased) member of the Vatican not to go public with his views. He was assured that his judgement had been accepted and that what remained on the Sistine Chapel ceiling of Michelangelo’s finishing auxiliary secco painting would be protected during the cleaning. With a catastrophically embarrassing professional schism averted, the restoration continued and the rest of what Tintori judged to be Michelangelo’s own auxiliary and finishing stages of painting was eliminated. Without knowledge of Tintori’s highly expert dissenting professional testimony, the public was assured that despite intense and widespread opposition the cleaning had received unanimous expert endorsement. Critics of the restoration were left prey to disparagement and even vilification.

On January 4th, we noted that in the widely reported schism that emerged at the Louvre with the resignations of Ségolène Bergeon Langle, the former director of conservation for the Louvre and France’s national museums, and, and Jean-Pierre Cuzin, the former director of paintings at the Louvre, from the Louvre’s international advisory committee on the restoration of Leonardo’s “Virgin and Child with St. Anne”, it had been recognised that the resulting crisis of confidence was of a magnitude not seen since the Sistine Chapel controversy. Restoration advisory committees are not imposed on museums and customarily they serve as political/professional fig leaves. In the wake of the Louvre committee resignations, embarrassed and perhaps panicky members of the museum’s staff offered self-contradictory and unfounded assurances (see below). In January, the Louvre’s head of painting, Vincent Pomarède reportedly claimed that “The recent cleaning was absolutely necessary for both conservation and aesthetical reasons.” This assurance proved unfounded on both grounds. Pomarède added that no member of the committee “has ever said that the cleaning was not prudent and had gone too far technically.” One has now done so – publicly – and left museum restorations under an unprecedented spotlight.

During an earlier cleaning controversy at the Louvre, Edgar Degas threatened to produce an anti-restoration pamphlet that would be what he termed a “bomb” – but he never did so, so far as we know. Now, as Dalya Alberge reports in the Guardian, the French Le Journal des Arts yesterday published an interview with Ségolène Bergeon Langle of truly momentous if not incendiary consequence (see below). We learn that her resignation came after no fewer than twelve letters requesting information on the restoration’s course went unanswered; that it was made in specific and pointed protest against the use of retouching pigments whose safety had not been proven; and, that the Louvre’s public claims of some pressing conservation need to remove the varnish were false, having been made despite it being known within the museum that any potential threat to the paint came not from the varnish but from a single faulty board in the picture’s panel which was reacting to the museum’s insufficiently stable environmental conditions. Perhaps most disturbingly serious for art lovers are Bergeon Langle’s disclosures that along with old (but nonetheless still protective) varnishes, original material of Leonardo’s was removed – against her advice – from the painting; and, aesthetically, that it is confirmed that the modelling of the Virgin’s face was weakened (see Figs. 1 and 2; and, for weakening to the modelling of St. Anne’s face, Figs. 12 and 13).

That the Louvre authorities would not inform even so distinguished a member of its own advisory committee might suggest either that the restorers had not known in advance what they would be doing to the painting; or, they feared that disclosure of their intentions would provoke opposition within the advisory committee. Either way, this was clearly an unacceptable (if not improper) way for a museum to execute irreversible alterations to one of Leonardo’s most advanced sophisticated, complex and problematic works. To Bergeon Langle’s now public “insider” criticisms, additional detailed material to highlight further Louvre procedural shortcomings and misrepresentations to the press and to the public will shortly be presented by Michel Favre-Felix, the president of the Association Internationale pour le Respect de l’Intégrité du Patrimoine Artistique (ARIPA). Favre-Felix is also to call formally for the establishment of a national scientific ethics committee that would be independent of museums and their restoration teams and be charged with re-examining the conservation file on the challenged St. Anne restoration.

A second member of Louvre’s advisory committee, Jacques Franck, the world authority on Leonardo’s painting technique, has said to the Guardian that a restoration likely to generate such disapproval from leading figures should never have been undertaken in the first place and, given that Ségolène Bergeon Langle is unquestionably France’s highest authority on restoration matters, her alarmed protest is therefore one that should mean a lot to both Leonardo scholars and art lovers the world over.

Unfortunately, the restoration-induced changes on the St Anne are not unprecedented. It is Art’s general tragedy that while scholars have quietly enlarged the oeuvre of Leonardo over the last century and a half, restorers have repeatedly swabbed and scritched away at the surviving fabric of those precious works – sometimes to an astounding degree, as with the “Last Supper” in Milan. With the National Gallery’s substitute version of the “Virgin of the Rocks” we have seen how the distinctive Leonardesque expression on the angel’s mouth was altered (without any acknowledgement) despite the fact that a distinguished scholar and former director of the Gallery, Kenneth Clark, had seen the angel’s face as being “the one part of our Virgin of the Rocks where the evidence of Leonardo’s hand seems undeniable, not only in the full, simple modelling, but in the drawing of the hair”. It is a matter of note that four of the most enthusiastically supportive members of the Louvre advisory committee were drawn from the curators and restorers who were directly responsible for the London and Milan Leonardo restorations.

Of Leonardo’s accepted earlier paintings, in 1939 Kenneth Clark lavished especial praise on the treatment of modelling found on two portrait heads – and in his enthusiasm, he awarded the palm of best preservation to both of them. The “Ginevra Benci”, then in the Liechtenstein Collection but now in the National Gallery of Art, Washington, was judged “the best preserved of all Leonardo’s early pictures”; one that “shows most clearly his intentions at this period”; and, one where “within the light oval of the face there is very little shadow, and the modelling is suggested by delicate gradations of tone, especially in the reflected lights.” Clark thrilled to the great refinement of execution: “We see a similar treatment of form in Desiderio’s low reliefs, controlled by the same sensibility to minute variations of surface. There are passages, such as the modelling of the eyelids, which Leonardo never surpassed in delicacy, and here for once he seems to have had none of that distaste for the medium which we can deduce from his later paintings, no less than from contemporary descriptions of his practice.” Ever aesthetically alert and deft, Clark saw all of these ultra-refined technical devices as being entirely “subordinate to the feeling of individual character with which Leonardo had been able to charge his portrait, so that this pale young woman has become one of the most memorable personalities of the Renaissance.” (We are grateful to Carroll Janis for drawing attention to this passage.)

Clark’s alertness to the physical/aesthetic characteristics of Leonardo’s hand was to the fore in his reflections on the “Portrait of a Musician” at the Ambrosiana in Milan. In the “subtle luminous modelling” of its head and its “delicate observation of light as it passes across the convex forms”, this work could only be “by Leonardo’s own hand alone and unaided” and it was “very similar to that of the angel in the Virgin of the Rocks”. As it stood before 1939, this too was “perhaps the best preserved of Leonardo’s paintings”, and in it we were then able to “learn something of his actual use of pigment, elsewhere obscured by dirty varnish, and we see that it was less smooth and ‘licked’ than that of his followers.”

Ironically, Clark, with his pathological aversion to “dirty” varnish (which is to say, old varnish on an old painting on an old support), was more responsible than anyone for the subsequent museum restoration/stripping mania. Looking around today’s museums, it is hard not to conclude that Clark might have been more careful in his wishes. Bergeon Langle’s warning against the modern addiction to penetrative imaging systems is particularly apt and timely: the hyper-active restoration changes (see right) made to the modelling and to the expression of those precious living Renaissance faces have cumulatively thinned and abraded pictures surfaces and material components and thereby remorselessly pushed great paintings into sad resemblances of their own infra-red under-states (see particularly, Figs. 4-11 and 19 & 20). Technical curiosity kills more than cats. In the case of Leonardo it has contrived to pull that artist back from his own increasingly lush highly-wrought subtly atmospheric shading towards the brilliant but thinner decorous linearity of Botticelli, when any comparison of the “Mona Lisa’s” hands with those of Leonardo’s “Annunciation” would have warned precisely against such perverse and regressive adulterations.

The interview given to Le Journal des Arts of 27 April, by Ségolène Bergeon Langle read as follows:

Why resign from the Louvre’s scientific advisory committee for the St Anne? “In January 2011 the committee had agreed on a gentle cleaning of late varnishes and the removal of the stains on the Virgin’s cloak. Yet, between July and October 2011 a more pronounced cleaning was done and presented as ‘necessary’, which I objected to. I was then faced with people who would oppose my position, which is technical and not based on aesthetics. My 12 letters [to the Louvre] asking for precisions on some aspects of the cleaning process and on the materials to be used for retouching, remained unanswered. I had to resign (on December 20th, 2011) to be heard just on one specific point: the Gamblin retouching pigments were not to be used since their innocuousness is not proven. Right from the beginning, false ideas have been put forth, like calling ‘repaints’ original retouches by Leonardo in the work’s early stages, or to attribute flaking in the paint layer to the ‘contracting varnish’, a [consequence that was] actually due to the sawing up of the wood [panel]…”

What do you think of the work done? “In my opinion, the precautionary principle hasn’t been respected. We must face the fact that the Virgin’s face is less modelled now. The cleaning should never have gone so far. However, I was happy that the grove [of trees] be preserved and, also, the ground’s material constituents that some ‘felt’ not original (though between January and April 2011 a brown-greenish section of the ground, located below St Anne’s elbow had been removed already). Besides, another matter of much controversy, the whitened layer on Christ Child’s body, has mistakenly been understood as a late varnish [that has] gone mouldy. I’m inclined to believe it was an irreversibly altered [original] glaze and, therefore, I have recommended that it be preserved, but nobody would hear me.”

The current Leonardo exhibition implies that his other paintings in the Louvre should be cleaned also. How do you feel about that? “Just not to do it, by all means! The original flesh paint in the St John-the-Baptist, being rich in oil, displays a significant network of drying cracks and might be fragile in the event of cleaning. For sure, scientific methods are essential but they need sound interpretation and wisdom dually… To date, there is too much boldness originating mistakes and an alarming fascination for infra-red investigation whereby are revealed under-layers that were never meant to be seen.”

Michael Daley

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Above, Fig. 1: The Virgin (detail) from Leonardo’s “Virgin and Child with St. Anne”, before restoration.
Above, Fig. 2: The Virgin (detail) after restoration.
Above, Fig. 3: Left, the short Louvre catalogue, published in 2012 after the restoration; right, a plate of the same heads published in 1992.
Above, left, Fig 4: Leonardo’s “The Musician” as published in 1945. Above, right, Fig. 5: an infra-red photograph of the musician published in 2011.
Above, Fig. 6: The musician, as in 1945. Above, right, Fig. 7: the musician, as published in 2011. By any optical appraisal, it can be seen that Leonardo’s painting presently stands somewhere between its 1945 self and an infra-red photograph of itself.
Above, Fig. 8: The musician, detail, as recorded in 1945.
Above, Fig. 9: The musician, detail, as found in 2011.
Above, Fig. 10: The musician, detail, as recorded in 1945.
Above, Fig. 11: The musician, as found in 2011.
Above, Fig. 12: The eyes of St. Anne, in Leonardo’s “Virgin and St. Anne”, before its cleaning at the Louvre.
Above, Fig. 13: The eyes of St. Anne, as found after the picture’s cleaning at the Louvre.
Above, Fig. 14: The eyes in Leonardo’s “Ginevra Benci”, as seen in Bode’s 1921 Studien über Leonardo da Vinci.
Above, Fig. 15: The eyes of “Ginevra Benci”, as found in 2011.
Above, Fig. 16: Andrea del Verrocchio’s “Flora”.
Above, Fig. 17: “Ginevra Benci”, detail, as seen in 1921.
Above, Fig. 18: “Ginevra Benci”, detail, as seen in 2011.
Above, Fig. 19: The musician, detail, as found in 2011.
Above, Fig. 20: The musician, detail, as found in 2011.
Can all the photographs in the world be wrong?
Might anything ever count as a fair demonstration of a restoration-induced injury?
Can no curator or trustee appreciate the inherent physical dangers when allowing restorers, who work with sharp instruments and highly penetrating solvents from the top down, to act upon pictures which artists have built from the bottom up in order to leave their finest and most considered effects exposed at the picture’s surface? Can no one in authority appreciate that every authorised restoration is an accident waiting to happen?
Does no curator ever wonder what has happened to eyebrows and the shading around eyes – and mouths, and nostrils – when pictures are “cleaned” or “restored”? Does no curator appreciate the vital function that shading serves for artists who are attempting to capture from nature, or to evoke imaginatively, a precise and specific personality, state of mind, engagement with the world? Does no curator recognise the tell-tale signs when restorers subvert artistically conjured forms and change the expression on subjects faces?
Would Kenneth Clark, if he were alive today, still consider “Ginevra Benci” and “The Musician” to be Leonardo’s best preserved works – and if not, why not? In the art trade it is recognised that the best preserved works are those that have been preserved least often by “conservators” and “restorers”. Why do people who are charged with protecting art in within the museum service so often take a contrary view? What supports their apparent belief that a much or a radically restored work may count as a “best preserved” specimen?
They all use the words freely, but do any Leonardo scholars, or Leonardo exhibition organisers, truly comprehend the vital conceptual connection between an artist’s system of illusionistic shading and the forms that sculptors literally build? Are any scholars prepared to discuss the manifest changes to Leonardo’s works that emerge in each successive monograph? The elephant in the art restoration room is this: while photography and book reproduction methods improve ceaselessly (see in particular the excellent and instructively enlarged photographs in Giovanni Villa’s Leonardo da Vinci – Painter, The Complete Works), authors themselves habitually refrain from discussing the nature of the often profoundly altered states to which their photographs testify. Ségolène Bergeon Langle, a conservation scientist, has bravely lifted the lid. Will others now discuss what lies below?
Click on the images above for larger versions. NOTE: zooming requires the Adobe Flash Plug-in.


Brighter than Right, Part 2: Technical Problems of Protection, Health and Safety at St Paul’s Cathedral

July 5th 2011

On June 15th the BBC news website reported that a £40m 15 years long restoration of St Paul’s cathedral by “state-of-the-art conservation techniques” had recovered Sir Christopher Wren’s “original vision” and left the building “as fresh as the day it was completed”. Major restorations invariably generate breathless accounts of recovered original glories made by vanquishing the “grime of centuries” – but grime only ever dates back to the previous restorations. At St Paul’s these were in the early and late twentieth century and the proposals for this last restoration explicitly declared that far from returning the interior to Wren’s original painted scheme, it would be stripped to a never-intended, never encountered state of bare-stone whiteness – see Part 1. As for the operation being “state-of-the-art”, consider these defensive/confessional remarks by David Odgers, of Nimbus Conservation, in 2005 just after the remains of Wren’s paint had been stripped: “Being completely inexperienced in the use of the material at the beginning, the learning curve was steep and problems of protection, health and safety issues and night time application had to be addressed”. This is the story of that learning curve.

The method used for cleaning the St Paul’s interior was novel and experimental but as such it was unproven. In both its composition and its effects it earned censure from leading conservation experts (see below). The cleaning agent was an adapted, commercially available, latex rubber poultice laced with a mix of chemicals that were said to comprise an agent tailored to be similar to the mild alkalinity of Portland stone – a special version of the “Arte Mundit” water-based paste manufactured by the Belgian company FTB Restoration. The instigator/director of the restoration, the architect and the 17th Surveyor to the Fabric at St Paul’s Cathedral, Martin Stancliffe, admitted (at a lecture on October 21st 2003) to having slim knowledge of matters chemical and of having devolved – “entrusted” – responsibility for the application of the new paste to the Nimbus conservators (who were learning on the job while the cathedral remained in full commercial and ecclesiastical use).

This state arose despite Mr Stancliffe’s boast that Nimbus had been selected as contractors after “the optimum formulation of the material had been achieved.” In practice, Nimbus, being entirely unfamiliar with this supposedly thoroughly researched and tested material, found its application by hand to be “slow, messy and to leave a streaky appearance on the cleaned stone.” Thus, when this multi-million pounds single-sponsor restoration was approved and underway it was discovered that: a) the result would look awful; b) it would take forever; and, c) it was leaving a terrible smell (of ammonia) throughout the cathedral.

With the restoration in full progress, the manufacturer went back to the drawing board and radically changed the paste’s approved composition and method of application. It has not been made clear of what the chemical changes consisted or whether approval for them was obtained (see below). With thousands of square metres of stonework to be cleaned, FTB Restoration devised what Mr Stancliffe and Mr Odgers described as “a method for spraying on the material using compressed air with a specially designed pump and nozzle”. This enabled each restorer to apply in “only a few minutes” up to 3.5kg of chemically laced latex paste per square metre (See Figs. 1,2,3,4 & 5). The industrial speed of application – between 50 and a 100 square metres a night – and, with it, the wider commercial prospect of buildings remaining open to business during interior restorations, caused great excitement in the upper tiers of heritage administration. With 2m visitors a year to St Paul’s and admission charges then at £6, now at £14.50, closing St Paul’s during the interior restoration would likely have lost something in the region of £50-60m, but, as we will see, the technical “solutions” to the initial unanticipated problems created serious consequences of their own.

Approval for the Arte Mundit cleaning method had been given by The Cathedrals Fabric Commision for England in November 1999 following claimed earlier approvals by a bevy of heritage watchdogs: English Heritage; SPAB – The Society for the Protection of Ancient Buildings; The Victorian Society; and The Georgian Group. It is not possible to establish the precise chemical basis on which formal approval was given by the CFCE because, in breach of good conservation practice, the three technical parts of the eight parts submission document have been withheld on grounds of commercial confidentiality. For information on technical matters we must rely on the cathedral’s own fluctuating (and self-contradicting) published accounts, on our correspondence with Mr Stancliffe (which was terminated by him in March 2003), and on documents obtained by cathedral employees whose health was affected by the restoration (see below).

In December 2002, Mr Stancliffe and Mr Odgers gave a joint account of the ongoing restoration in Conservation News. They explained why the Arte Mundit poultice method had been adopted and why the so-called “Mora Poultice” method had been rejected. It might be noted that the latter is a cocktail of thixotropic paste, sodium bicarbonate, ammonium bicarbonate, detergents and the aggressively powerful chelating agent EDTA – ethylene diamine tetra-acetic acid. That poultice had been designed for cleaning marble buildings and was used experimentally on Michelangelo’s Sistine Chapel ceiling frescoes to disastrous effect (see our post of April 1st). By 1992 research had shown that the brightness produced was not a product of marble surfaces having been cleaned but of their being etched by the EDTA into dissolved irregularities which scatter light in all directions.

It was thus known before this restoration began that consuming stone is a consequence of EDTA levels being either too high or left too long on the surface. The Mora poultice was also rejected because the copious amounts of water needed to remove it would have turned St Paul’s Portland stone brown when, as we saw in Part 1, Mr Stancliffe’s ambition was to produce white stripped-stonework in defiance of Wren’s original warmly toned oil painted decorative scheme.

Mr Stancliffe and Mr Odgers reiterated in their joint Conservation News article, that the chemical composition of their Arte Mundit paste had been “specifically formulated” after a great deal of research (but by then the research seemed to have run into the restoration itself). While it had been found necessary at the outset to add EDTA to the latex paste, they said, this had been done only “at a concentration of 2000mg/kg (0.2%)” precisely to avoid injuries to stone when used at solutions of 11% in the Mora poultices. Before discussing the hugely varying EDTA levels seen to have been used at St Paul’s, consideration should be given to Arte Mundit’s initial principle cleaning ingredient – the pungent alkali ammonia.

Sprayed applications compound the health risks associated with hazardous chemical products. Although Mr Stancliffe and Mr Odgers admitted “the downside of using compressed air is that the Arte Mundit is applied as a fine particulate and releases ammonia into the atmosphere”, they seemed to regard this as a nuisance rather than a threat to health. Until then, as they put it, the paste had “contained ammonia” but, because “St Paul’s is visited by thousands of people each day, it would be inappropriate for the Cathedral to smell of ammonia.” They added that “Recent developments have meant that the concentrations of ammonia have been significantly reduced in the Arte Mundit so that potential risk has been minimised.” It was not there said of what the “developments” consisted or to what figure the ammonia had been reduced, but it was admitted that atmospheric concentrations of ammonia (which is generally detectable at 4ppm) had reached 10ppm in the cathedral. Needless to say, reducing the smell of the most pungent chemical ingredient is not the same as eliminating or reducing the risks presented by all the chemicals present in the sprayed paste.

Sand blasting the interior surfaces had been rejected partly because installing absolutely airtight isolation to retain airborne dust would have been too expensive (see Figs. 4, 5, 6, 7, 8 & 9). In April 2003 a Health and Safety Executive officer (who was under the impression that the only change made to the Arte Mundit paste had been a reduction in its ammonia content and who seemed unaware that EDTA had been incorporated even though it was listed in the manufacturer’s safety data sheet to which she referred – see Figs. 10, 11 & 12) reported, in a seeming counsel of ineffectuality, that “In order to clean a large, old cathedral it is expected that dust will become airborne and it may be that this is contributing to the respiratory problems [of staff members]”. Despite not finding any trace of what she termed “EDA” anywhere in the cathedral, she had “asked the contractor to improve the ventilation in the work areas during the cleaning process.” (See Figs. 3, 4 & 5.) Quite mystifyingly, she added that this EDA, “was not a separate substance within the mixture but we wished to ensure that it was not produced as a by-product.

When in October 2002 a member of the cathedral’s staff who had suffered severe skin afflictions requested a copy of the manufacturer’s material safety sheet (Figs. 10, 11 & 12), she discovered that the paste was then containing EDTA at up to10% – which is to say, almost the same as in the discredited (and rejected) Mora Poultice, and therefore at up to fifty times greater than the figure shortly to be claimed by Mr Stancliffe and Mr Odgers in the December Conservation News.

That safety sheet was no rogue document. In March 2003, when declining to answer our questions on inconsistencies in the official accounts, Mr Stancliffe produced certain “fact sheets” which, he averred, “answered all potential questions which you or anyone else may have on this aspect of our interior cleaning programme.” The sheets (entitled “The Arte Mundit Fact File”) were models of un-clarity and consisted entirely of questions jointly put to the restorers and to the Arte Mundit manufacturer by themselves, along with the answers they gave to their own questions. Thus, to “What controls are in place to ensure that the application and removal of the Arte Mundit is competently handled?” (their question 23), Nimbus/FTB replied “The contract has been entrusted to a company run by and employing accredited conservators.” This circular defence would suggest that the restorers, even while learning on the job, were judged capable of monitoring their own performance as well as the performance and the safety of their untested and still evolving methods.

These “fact sheets” contain contradictory material. They give an account (in answer to their question 16, “Has the formulation been changed?”) of the manner in which Arte Mundit’s composition had been changed after the 1999 approval of its “optimal” formulation: “In the first fifteen months of using the material the concentration of ammonia was less than 0.5%. Further development of the product allowed to [sic] reduce the level of ammonia, which is now less than 0.005%.” This account prompts two concerns. First, the reduction of ammonia to one hundredth of its original levels is not confirmed in official restoration documents (see below). Second, in answer to question 16 it was also stated that, regardless of the claimed dramatic reductions of the ammonia level, “The level of EDTA was not changed and the efficacy of the product remained identical.” This beggars belief: there are two cleaning agents in the paste, one an alkali, the other an acid – ammonia and EDTA. If the former was reduced to a hundredth of its original level, how could the efficacy of the whole not have been diminished on the one hand, and slewed in its pH composition, on the other? And, for that matter, what is the level of the EDTA? There is no confirmation in the “fact sheets” of Mr Stancliffe’s and Mr Odger’s joint claim in the December 2002 Conservation News that EDTA was used at 0.2%. In answer to question 4 (“What are its [Arte Mundit’s] constituents?”), EDTA is mentioned as a component but no figure is given for it. In answer to question 7 (“Are there different types?”), it is said: “Yes there are five different types, Arte Mundit I, II, III, IV and V. These are similar except the concentrations of EDTA differ with the lowest concentration (less than 2.5%) being Type II and the Highest concentration being Type V. Arte Mundit I contains no EDTA.” So what type was being used at St Paul’s? To find an answer we must turn to question 15 (“What type is used at St Paul’s?”) where it is revealed that: “After tests carried out at St Paul’s Arte Mundit V was formulated by Dr Eddy de Witte to address the specific conditions found at the Cathedral.” But on this answer we learn that the type of Arte Mundit which contains the highest levels of EDTA (at up to 10%), Type V, was the very one that had been specifically developed for St Paul’s – so from where does the figure 0.2% derive? Had EDTA been required only at the Stancliffe/Odgers claimed level of 0.2%, it would surely not have been necessary to develop a special type of Arte Mundit at all, because the already existing Type II, containing EDTA levels of up to 2.5%, would more than have sufficed?

When a cathedral worker whose station was next to a cleaning area complained to the Clerk of the Works on May 13th 2002 that strong smells were affecting her throat, he prepared a report (see Fig. 13) on May 17th saying that he had asked Nimbus to “get details of material, and improve ventilation”. On that day, she fell sick and was off work for a fortnight with a blocked nose and a bad chest having reportedly been told by the Clerk “Don’t worry, whatever they were using has been banned, they shouldn’t have been using it”.

In the following August a Health and Safety Executive COSSH ASSESSMENT (Control of substances harmful to health – see Fig. 14) identified the main active components of the Arte Mundit paste as: “EDTA (<30%); ammonia (<0.5%)”, which is to say with ammonia still at its original (and not the claimed massively reduced levels) but with EDTA levels then at up to an astounding 150 times higher than Stancliffe and Odgers were to claim publicly in December 2002.

The consequences of exposure to the EDTA-laced Type V paste, as stated on FTB Restoration’s own Material Safety Sheet of August 16th 2001, (where EDTA levels were already put at 10% and not at the later claimed figure of 0.2% – Figs. 11, 12 & 13) were said to be: “irritating to eyes, respiratory system and skin”. The primary route of exposure was: “Skin and eyes contact. Vapours inhalation.” The symptoms relating to use were: through inhalation – “Sore throat. Cough. Shortness of breath”; by skin contact – “Redness”; by eye contact – “Redness, pain. Tears”; by ingestion – “Abdominal pain, nausea.

The staff member who had requested the safety sheet had recorded her own afflictions as they occurred. They made disturbing and progressively grimmer reading (– see Fig. 13). Because that member of staff had previously suffered from skin ailments, a specialist medical examiner who had been hired by the cathedral and who, (like the HSE inspector mentioned above) had accepted the claim that “the only change that was made [to the Arte Mundit] was to reduce the level of ammonia from 0.5% to 0.005% because of ‘the slight smell of ammonia that was present after the initial application’”, contended that her afflictions could not, “on the balance of probabilities”, safely be attributed to airborne chemicals in the cathedral. Nonetheless, he admitted that his decision might have to be reconsidered were “compelling further evidence in favour of occupational causation to be adduced”. This staff member had not been alone in her afflictions. In January 2003, a Press Association article (“Cathedral staff ‘have symptoms of chemical poisoning’”) reported that:

Staff at St Paul’s Cathedral have been falling ill with symptoms of chemical poisoning, it emerged today. The Health and Safety Executive is sending investigators to the London landmark after staff reported suffering chest pains, respiratory problems and skin complaints. Chief suspect is the substance being used to clean the stonework of the historic building as part of a £40million restoration project. Arte Mundit, a cream paste that removes stains and dust on most surfaces, is being sprayed on to the fabric of the building. It contains ammonia, the smell and intensity of which has prompted the cathedral authorities to carry out all spraying at night. The man in charge of the project, surveyor to the fabric, Martin Stancliffe, was not available for comment today…Another substance in the cleaning mixture that might be causing the health problems is latex – it can cause skin allergies, sneezing, throat irritation and asthma…St Paul’s Cathedral registrar John Milne said that 20 out of 150 people working at the Cathedral had reported conditions which might be related to the restoration…

In the March 2003 Conservation News, the St Paul’s/FTB Restoration method (as described there by Stancliffe and Odgers in December 2002) was challenged by conservation specialists. Professor Richard Wolbers, conservation scientist and solvents expert at the Winterthur Museum and Gardens, University of Delaware Art Conservation Department, charged the authors with appearing “not to understand very well the chemistry of the materials they are using” and of seeming to “resort to what I would call several common (and spurious) arguments to rationalise the ‘safety’ of their cleaning systems over other methods cited.” For example, he wrote, “EDTA is one of the strongest chelating materials one could bring to such a surface.” It would certainly dissolve “any calcium carbonate beneath it in the stone substrate that it may come into contact with…It is almost as if they simply adopted a commercial material that was easy to obtain or apply without considering what specific chemistry they were bringing with it to the stone surfaces or how it might affect the other constituents they might be adding.

Professor Wolbers was highly critical of a number of other technical features of the programme but reiterated his fear that the authors “seem to have taken a poorly characterised material, a latex paste, and modified it with the addition of a considerable amount of EDTA (largely as an adaption in their minds, I suppose, of one of the main ingredients in the Mora’s AB57 cleaning system).

John Larson, Head of Sculpture and Inorganic Conservation at the Conservation Centre, National Museums and Galleries on Merseyside, said that applications of moulding materials had contributed so much damage over the past 200 years that museums around the world “have now banned” their use, and that the application of liquid latex by brush or spray “has a dramatic effect on porous material such as stone…as it dries latex shrinks and clings tenaciously to the surface.” The effect of pulling it off the stone “exerts strong mechanical forces on the surfaces when the stone is carved and deeply undercut, as shown on the cover of Conservation News.” (See Figs. 1 & 2.)

Seemingly in the face of such attacks, accounts of the St Paul’s/FTB Restoration method shifted once more. In the May 2003 Conservation News Mr Stancliffe and Mr Odgers ignored Prof. Wolbers’ criticisms, which, they said, would be answered in a future article not by themselves but, instead, by the man who had developed Arte Mundit for the Belgian firm, Dr Eddy de Witte. Having said in December 2002 that “The original oil paint [of Sir Christopher Wren] is found to soften and can then be removed with water and scrubbing and this is both acceptable and desirable, as it is removing an unwanted and dirty paint layer”, Stancliffe and Odgers now insisted that Arte Mundit “is certainly not a paint stripper.” Apologising for having “misled” readers on the point, the pair claimed that when they had said “original oil paint” they had not been referring to the original oil paint but to “subsequent distemper applications and not to the original paint.” The distemper “is indeed softened by the latex”, they added, “as it would be by soaking with water”. At this point they admitted that the paste contained EDTA but gave no indication of whether it was at solutions of up to 0.2%, 10% or 30%.

A key concern of conservationists facing such methodological discrepancies was whether or not the EDTA migrated into the stone during the periods of curing after being sprayed as a water-bound paste on to porous surfaces that had already been attacked with caustics and abrasives by previous restorers. With regard to Prof. Wolbers’ fear that Arte Mundit’s EDTA would have the time and the opportunity to invade and damage the stone yet another set of Stancliffe/Odgers claims was revised. In their May 2003 account, they claimed that the latex solution was sprayed to a depth of only 2mm and left for only “two or three hours” when in December 2002 they had said that the curing lasted “usually 24-48 hours”. In May 2002, Conservation News reported that the latex was removed after “one to four days”. In April 2003, the BBC reported that the latex was left on the stone surfaces for between “One to four days [depending] on the thickness and temperature”.

In December 2002, Stancliffe and Odgers had claimed that after removal of the Arte Mundit paste and subsequent washing and scrubbing, the stonework “still retains a patina”. In May 2003 they admitted that John Larson had rightly pulled them up for their “inappropriate use of the word”. Today the surface of the stone can be seen to have been left porous, susceptible to invasion by pollution, and chalky. Its weakened surface can now be rubbed away with a wipe of dry cloth – see Figs. 15 and 16.

Michael Daley

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Fig. 1, above: a conservator removing a latex “cleansing pack” from a carved head at St Paul’s Cathedral, as published on the cover of Conservation News in May 2002. The journal reported that the latex was left on the surface for “one to four days” and that after its removal, the stone was cleaned with “damp sponges and bristle brushes“.
Fig. 2, above: a carved head at St Paul’s after being cleaned with water and bristle brushes – as shown on the back cover of the programme to a Choral Evensong service in honour of the Donors to the Cathedral’s 300th anniversary appeal on June 1st 2005, after the completion of the cleaning of the cathedral’s interior. (Photography by Peter Smith/Jarrold Publishing.)
Fig. 3, above: a Nimbus conservator spraying Arte Mundit Type V latex paste onto carved decorations at St Paul’s Cathedral, as shown on the BBC’s science programme “Tomorrow’s World” on April 24th 2002. The programme reported that the latex was left was left to “cure” on the stone for “between one and four days”, depending on the thickness and temperature. Notice the thickness of the overhanging latex accumulations. It was later claimed in the 2003 “Arte Mundit Fact File” that spraying was applied to “a maximum thickness of 2mm”.
Fig. 4, above: a (better protected) Nimbus conservator spaying Arte Mundit paste at St Paul’s Cathedral, as shown in the programme to the celebratory June 2005 Choral Evensong.
Fig. 5, above: a photograph of the Arte Mundit spraying system that shows the path of the extraction ducting through a window at St Paul’s Cathedral. Note the fallen polythene sheeting (which is meant to isolate the spraying zones from the rest of the cathedral) to the left of the ducting. In “The Arte Mundit Fact File”, Question 10 (“What precautions are taken to keep the area being sprayed enclosed?”), it said that “Each spraying is encapsulated with polythene sheeting to prevent any possibility of the material getting outside of the scaffold area. A secondary protection is provided by the monarflex sheeting around the scaffold.”
Fig. 6, above: a section of monarflex sheeting descending from a spraying area in the South Transept during 2002.
Fig. 7, above: a section of monarflex sheeting under the Dome.
Fig. 8, above: a section of monaflex sheeting under the Dome.
Fig. 9, above: a section of extraction ducting carrying fumes and fine sprayed latex and chemical particulates outside of the cathedral.
Fig. 10, above: the first page of FTB Restoration’s Material Safety Data Sheet for its Type V Arte Mundit latex paste, as then being applied on the interior of St Paul’s Cathedral. Note, the sheet is dated August 16 2001 and is thus four months into the cleaning campaign. EDTA is shown to be at solutions of up to 10% and ammonia is being used at solutions of up to 0.5%. The product is seen to be “irritating to eyes, respiratory system and skin”; to cause “Sore throat. Cough. Shortness of breath. Redness, pain. Tears”, and, if ingested, “Abdominal pain, nausea.”

The member of St Paul’s staff who asked for the Arte Mundit Material Safety Sheet kept a log on her own ailments until her early retirement on June 12th 2003 because of her declining state of health. Her notes began on October 1st 2002:

01/10/02: Became very hot and itchy. By end of day a red rash covered my arms and chest. The itching was intense and I could not sleep. 03/10/02: Rash extended now to back. Went to GP – also saw nurse. Given anti-histamine pills and steroid cream – went to work for the rest of the day. 04/10/02: After work, went back to GP as rash still spreading fast and felt very ill. Given another type of pill plus different creams and a blood test. 07/10/02: First day of duty. Felt very unwell, cancelled a visit to my mother and went to GP once more. Again, they are very worried and put me onto steroid pills. I could not sleep at all at night due to the constant irritation which was now causing me major distress. 10/10/02: While on my days off duty, I had started to feel better – lot less hot and itchy. However, this is my first day back on rota and start to itch and become very hot and unwell. Went to see […] our personnel manager. She was on her way to a meeting, but promised to get back to me later in the day. This did not happen. 11/10/02: After an unbearable night, went into work despite feeling very unwell. Went to see the registrar, John Milne and asked that he contact Health and Safety, as by now other members of staff had… 14/10/02: Saw doctor at hospital. She was very concerned and asked if it were possible to obtain a detailed list of constituents of the cleaning agent, as the COSSH assessment we were given was of little use. The rash was too active to allow any tests to take place…11/11/02: Went to GP. Actual allergy now seems unlikely. However, it seems I have been rendered extremely sensitive to the cocktail of toxic chemicals used at work, resulting in a severe attack of industrial dermatitis, which has left my skin in a very damaged condition…”

Fig. 11, above: the second page of FTB Restoration’s Material Safety Data Sheet for its Type V Arte Mundit latex paste.
Fig. 12, above: the third page of FTB Restoration’s Material Safety Data Sheet for its Type V Arte Mundit latex paste.
Fig. 13, above: a Health and Safety Executive COSHH (Control of substances harmful to health) Assessment of the Arte Mundit paste being used at St Paul’s Cathedral on August 8th 2002 (fifteen months into the restoration of the interior). Note that, at that date, the main ingredients identified were EDTA, which was being used at solutions of up to 30%, and ammonia, which was being used at up to 0.5%.
Fig. 14, above: an internal St Paul’s Cathedral Report of Hazard or Defect, issued on May 17th 2002 by the cathedral’s Clerk of the Works in request of information on materials being used, and calling for improvements to be made to ventilation.
Fig. 15, above: the sleeve of the author’s jacket as photographed in the South Transept of St Paul’s Cathedral on July 1st 2011.
Fig. 16, above: the sleeve of the author’s jacket after being brushed against stonework seven feet from the ground, in the South Transept on July 1st 2011.

The conservator John Larson (see left) had warned in the March 2002 Conservation News that “Anyone who has worked with care on the conservation of historic stone surfaces will be aware that there are always hidden weaknesses and cracks that will often only be revealed when pressure from cleaning systems such as water, abrasives and steam are applied. To use a technique that subjects a historic surface to unnecessary pressures (as with Arte Mundit) cannot be described as conservation or innovation…With all stone cleaning it is sensible to avoid the introduction of extra chemicals which can cause irreverisble damage.

Mr Larson cited the cautionary example of Glasgow where a rash of chemical cleanings caused a rapid growth of salts which turned the affected buildings green. He added: “The damage was so bad that a moratorium was called on all stone cleaning in Scotland.

Fig. 17, above: a member of the specialist decoration firm Hesp and Jones recreating one of the fictive swags that formed part of the original decorative scheme of the Tambour – the truncated conical band of windows and wall on which Thornhill’s painted Dome rests. This recreation constitutes one of the most successful treatments at St Paul’s. It merits and will receive separate discussion.
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Misreading Visual Evidence ~ No 2: Michelangelo’s Sistine Chapel Ceiling

April 1st 2011

No single proof of a restoration-induced injury to a work of art could be clearer than the photograph shown here (Fig. 1) of a section of Michelangelo’s Sistine Chapel ceiling frescoes. It was taken after the last restoration and shows in its centre section a repair made in 1566 by the painter Domenico Carnevale when a section of Michelangelo’s fresco fell away during settlement of the building (see Fig. 2 diagram). Carnevale had re-plastered the loss and, while the plaster surface was still wet, faithfully painted it to match Michelangelo’s (then) surrounding colours and tones. The repair was a good one and for centuries it remained almost invisible (see Figs. 4, 5 & 6). Ever since the last restoration it has been glaringly evident that Carnevale’s painted section no longer matches what has survived of Michelangelo’s painting (see Fig. 7). As will be shown, on the evidence of these photographs, fair estimation can be made of the injuries inflicted upon Michelangelo’s frescoes during restoration.

The reason why the photographs testify to restoration injury is simple and elegant. Carnevale’s repair was made a fresco in “good” or buon fresco, which is to say, solely with pigments that were painted onto the still-wet plaster and, crucially, without any later additional painting on the surface of the fresco after it had dried. With this method, Carnevale matched the pictorial values of Michelangelo’s frescoes as they were then found, only half of a century after their completion. However, unlike Carnevale’s painting, where the pigments were locked into the lime plaster when it dried, Michelangelo’s own frescoes were completed a secco – that is to say, with much additional glue or size-based painting applied to the surface of the frescoes after they had dried. Against great evidence (see below), the Vatican’s restorers concluded that Michelangelo had painted entirely in buon fresco without a secco additions and, on that (unsound) decision, they contended that it would be perfectly safe to apply a recently developed oven cleaner-like thixotropic cocktail of cleaning agents (in two applications of three minutes duration each, each being washed off with copious amounts of water) that had been designed to strip polluted encrustations from marble buildings and that would most certainly strip all organic material – which in the event would include Michelangelo’s own glue-based painting – from the ceiling’s plaster surface.

Because Carnevale’s own painted repair was not so vulnerable we now see in the repaired (centre) section a better record of how Michelangelo’s own painting had appeared than exists in the surviving sections of Michelangelo’s painting. By properly reading the testimony of this photographic record, we can calculate the scale of loss that ensued when Michelangelo’s own a secco work on the surface of his frescoes was removed.

By that method, Michelangelo had painted shadows onto his figures after the plaster had dried. After the recent removal of those shadows a figure emerged (as seen right) with arms that were apparently depicted flatly and without tonal modulation in a single local colour/tone by Michelangelo on either side of a section by Carnevale where the forms of the arms were fully modelled by dramatic shading. Could that ever have been the case? Would Carnevale have been allowed to conduct a master-class demonstration to Michelangelo on how to render painted forms sculpturally? Those who still defend this restoration – as some British newspaper art critics do – might attempt to offer some credible explanation for this startling visual and plastic mismatch, which presently stands as the largest elephant in the art restoration room.

The crime against art that this restoration constituted was compounded by art historical apologists who claimed that the Michelangelo everyone for nearly five centuries had thought existed, had never existed, and that a new, true Michelangelo who, far from being “essentially a sculptor” was “one of the great colourists of Western Art”, had been uncovered by courtesy of a single cleaning. To justify this historically revisionist and artistically subverting “outcome”, apologists for the restoration were obliged to offer one of the most cockamamie art historical/technical accounts: namely, that what had “deceived” Michelangelo’s own contemporaries and everyone else for nearly five centuries had been nothing more than the effects of dirt and soot that had slowly and imperceptibly accumulated on the ceiling’s frescoes over the centuries.

This deceiving filthy material had, the artistically credulous are invited to accept, artfully arranged itself around Michelangelo’s flat, bright, “colouristic” designs so as to mimic the effects of the very sculptural preoccupations for which Michelangelo was already famed. In due course, it was further suggested, this artful dirt and soot had been set in glue by successive restorers, who, on one occasion, it is said, did so while standing on the top of thirty feet high step-ladders while brandishing glue-filled sponges tied to the end of thirty feet long poles. When the Vatican authorities were challenged on this account (by us) they had to admit that no proof existed of any glues ever having been applied by any restorers. What the Vatican authorities might also have admitted is that a further indisputable technical proof of Michelangelo’s authorship of the glue-painting on the fresco surface had emerged in the 19th century when the Vatican made its own moveable scaffold available to the British painter Charles Heath Wilson – and that this testimony was known to them. On examining the ceiling, Wilson had found that:

“…the frescoes are extensively retouched with size-colour…evidently by the hand of Michelangelo”.

Wilson could not only see this glue painting on the plaster surface, he could touch it:

The colour readily melted on being touched with a wet finger and consisted of a finely ground black, mixed with a size…The shadows of the drapery have been boldy and solidly retouched with this size colour, as well as the shadows on the backgrounds. This is the case not only in the groups of the Prophets and the Sybils, but also in those of the Ancestors of Christ in the lunettes and the ornamental portions are retouched in the same way. The hair of the heads and beards of many of the figures are finished in size colour, whilst the shadows are also thus strengthened, other parts are glazed with the same material, and even portions of the fresco are passed over with the size, without any admixture of colour, precisely as the force of water colour drawings is increased with washes of gum…These retouchings, as usual with all the masters of the art at the time, constituted the finishing process or as Condivi expresses it, ‘l’ultima mano’.”

In addition to his expert (i.e. artist’s) testimony, Wilson offered two further material proofs of Michelangelo’s authorship that might otherwise have been expected to be considered clinching by today’s “scientific” restorers:

They [the retouchings] were evidently done all at the same time and therefore when the [original] scaffold was in its place.”

There can be no doubt that nearly all of this work is contemporary, and in one part only was there evidence of a later and incapable hand. The size colour has cracked as the plaster has cracked, but apart from this appearance of age, the retouchings have all the characteristics of original work.”

It is a matter of record that the ceiling cracked before any restorers went near it. If the size painting cracked with the plaster, it must have predated the cracking – and, therefore, also that of any restorer’s intervention. Or, to reverse the testimony: if the glue had been applied by restorers long after Michelangelo had painted the ceiling and long after the ceiling had cracked, as has been suggested, it would have run into the already extensive cracks – but it was not and it had not. We can thus be in no doubt that today’s restorers removed the final stages of Michelangelo’s own work; that the “New Michelangelo” they had “discovered” was nothing more than the mutilated remains of his original work that they had left on the ceiling; that no part of the ceiling had escaped the consequences of their labours.

The last restorers of Michelangelo’s ceiling frescoes seem not fully to have heeded the cautionary evidence of their predecessors’ mishaps. The warnings – both pictorial and documentary – were clear enough. We see in the photograph of the left hand of God from Michelangelo’s “The Separation of the Earth from the Waters” (Fig. 10) that there is today a great mismatch between the sleeve and the fragment of cuff that had been repaired by Carnivale. Engraved copies of the 18th and 19th centuries (see Figs. 8 & 9) suggest that losses of shading to God’s left arm preceded the latest restoration. Charles Heath Wilson, who complained of the ceiling’s filthy and neglected condition and believed that it would profit from cleaning, nonetheless warned in terms against any watery interventions. Not only had he found Michelangelo’s size-painting vulnerable to a wetted finger, he complained that parts of the ceiling had already “undoubtedly been injured by rude [restoration] hands, suggesting that glazing has been partially or entirely swept away” and that great restoration injuries had previously occurred when the ceiling had been “washed by labouring men with water in which a caustic has been mixed”. (For details of the recent water-based cleaning methods, see bottom right.) The consequences of water injuries had been set out by Wilson:

Thus great brushes or sponges have been swept over the skies and backgrounds and have not only removed dirt in a coarse unequal way, but have eaten into the colours and destroyed them in a variety of places. The Face, shoulder and arms of the prophet Daniel, various parts of the bodies and limbs of the young men sitting over the cornice and other portions of the frescoes have been nearly obliterated by this savage proceeding. The Injury done is irremediable, for the surface of Michelangelo’s work has been swept away.

Michael Daley

For a full account of the ceiling’s injuries, see “Art Restoration ~ The Culture, The Business and The Scandal”, London 1993 and 1996, New York 1994, by James Beck and Michael Daley.

For evidence of injuries to the prophet Daniel, see our post of January 23rd 2011.

Comments may be left at: artwatch.uk@gmail.com

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Above, Fig. 1: a detail from one of Michelangelo’s Sistine Chapel pendentives, “The Punishment of Haman”, containing, in its centre section, a repair made made by the painter Domenico Carnevale in 1566.
Above, Fig. 2: a diagram in which the parts of the figures of Esther and the king Ahasuerus that were repainted by Domenico Carnevale in 1566 are indicated by dotted lines in the centre section.
Above, Fig. 3: a detail showing, in the centre section, the arms of Esther as restored in 1566 by Domenico Carnevale.
Above, Fig. 4: the left-hand section of Michelangelo’s pendentive depicting “The Punishment of Haman”, as seen before the last restoration. Note the close conformity between the tonal/shadowy zone occupied by the figures as seen here and that recorded in the engraving of 1796 by Domenic Cunego in Fig. 6.
Above, Fig. 5: the left-hand section of the pendentive “The Punishment of Haman”, before cleaning.
Above, Fig. 6: the pendentive “The Punishment of Haman”, as engraved in 1796 by Domenic Cunego. Note particularly, here, the skilful placement of the darkest tones in the three corners of the pendentive. And, the masterly use of light and shade to articulate the roles of the principal and secondary figures. Pulling the (very sketchily drawn) group at the left out of their original shadow, as occurred in the recent restoration, did them no favours and did great violence to the disposition of Michelangelo’s own pictorial values. Few will doubt that Michelangelo had intended to place the greatest possible emphasis on his central crucified figure – an invention which constituted an astonishing tour de force in its day by means of the violent planar opposition of the knees, which are parallel with the picture plane, to that of the hands, which contrarily advance upon it at a near right angle. This great figural innovation is emphasised by the artist in the similarly acute foreshortening of the wall to the right of Haman.
Above, Fig. 7: the figures of Esther and King Ahasuerus, after restoration.
Above, Fig. 8: Michelangelo’s depiction of God in “The Separation of the Earth from the Waters”, as engraved by Domenico Cunego, 1772-1780. Note the remarkable similarity between the shading of God’d left arm and that reproduced by Carnevale in his treatment of Esther’s arms.
Above, Fig. 9: Michelangelo’s “The Separation of the Earth from the Waters”, as engraved by Attilio Palombi in 1887.
Above, Fig. 10: The left hand of God in “The Separation of the Earth from the Waters”, after the recent cleaning. The diagonal crack entering at the top, centre, bounds the area of Carnevale’s restoration of the hand and part of the cuff, made in accordance with the tonal values found on the figure in 1566.
For a celebration of the restored ceiling, see “Michelangelo ~ the Vatican Frescoes” by Pierluigi de Vecchi, Professor of Art History at the University of Macerata, and Gianluigi Colalucci, Chief Restorer, Vatican Laboratory for the Restoration of Paintings, Papal Monuments, Museums and Galleries, New York, London and Paris 1996.
For a celebration of the restoration and an account of its cleaning methods, see “The Sistine Chapel ~ Michelangelo Rediscovered” with contributions from: Carlo Pietrangeli, Director General of the Papal Monuments, Museums and Galleries; Professor Andre Chastel; Professor John Shearman; Professor John O’Malley, S.J.; Professor Pierluigi de Vecchi; Professor Michael Hirst; Fabrizio Mancinelli, Curator of Byzantine, Medieval and Modern Art, Papal Monuments, Museums and Galleries; Gianluigi Colalucci, Head Restorer, Laboratory for the Restoration of Paintings, Papal Monuments, Museums and Galleries, published London, 1986.
The cleaning method here identified reads in part: “…Removal of retouchings and repaintings with a mixed gelatinous solvent, consisting of ammonium bicarbonate, sodium bicarbonate, Desogen (a surf-actant and anti-fungal agent), carboxymethylcellulose (a thixotropic agent), dissolved in distilled water. Mixture acts on contact. The times of application, rigorously measured, were: First application: 3 minutes, followed by removal, washing with water. Left to dry for 24 hours. Second application: 3 minutes, followed by removal, washing and leaving to dry as before. If necessary, and locally only, small applications, followed by plentiful final washing. In the case of salt efflorescences consisting of calcium carbonate, there was added to the solvent mixture a saturated solution of dimethylformamide…
Final treatment: the thorough, complete and overall application of a solution of Paraloid B72 diluted to 3% in organic solvent, removed from the surface of the pictorial skin by the combined action almost simultaneously of organic solvent and distilled water, which coagulates the surface acrylic resin dissolved by the solvent.”
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