The Restoration of Leonardo’s Last Supper

The Troubled Story of Leonardo’s Last Supper

By Jeffrey Morseburg

            When a tourist visits one of the great historic cities of Europe, there are sites and objects that are considered a “must see” in each place. If you spend any time in Paris you know that new visitors have to take that ride to the top of Gustav Eiffel’s Tower, the triumph of the Industrial Age and visit the Louvre with its acres of picture galleries. Once they walk down the steps of I.M. Pei’s controversial entrance to the Louvre, legions of tourists make a beeline for the classical sculpture “Venus de Milo” and the most famous painting in the world, Leonardo Da Vinci’s “Mona Lisa.”  In Rome it’s the Coliseum that is considered a “must see” and in Milan, in the industrial heart of Northern Italy, it’s the dramatic Duomo Cathedral and Leonardo’s “Last Supper” the that tourists flock to. When visitors rush to gain admittance to see the “Last Supper” they may know that since soon after it’s inception it has been considered one of the “masterpieces” of western art but they soon discover that it has long been obscured by decay and one botched restoration after another.  Only have they have been allowed their fifteen minutes to gaze at Leonardo’s dramatic painting of Christ and his discliples, do they fully realize that there is actually precious little of what the master painted five centuries ago left on the wall… and that without the extraordinary and expensive measures that have been undertaken in recent decades, what remains of Leonardo’s handiwork would soon disappear.  The truth is that from the very start the planets the artist and pioneering scientist liked to observe seemed to be aligned against the most ambitious work Leonardo managed to complete.

The Prologue

Leonardo Da Vinci (1452-1519) was an illegitimate child who came from Vinci, a town just outside the city of Florence, in the beautiful hills of Tuscany, overlooking the Po River Valley.  In those days of independent Italian city-states, Florence was a nominally a republic with a democratic form of governance. In actuality the beautiful city on the winding river Arno was actually under the thumb of the powerful and manipulative Medici banking family and its head, the legendary patron of the arts Even though he was not formally educated, Leonardo was a precocious young man with a brilliant intellect, an insatiable curiosity and an extraordinary talent for drawing and sculpting. At fourteen he was apprenticed to his father’s friend Andrea del Verrocchio (1435-1488) a master painter, sculptor and goldsmith in the employ of the Medicis. In those days of independent Italian city-states, Florence was a nominally a republic with a democratic form of governance. In actuality the beautiful city on the winding river Arno was under the thumb of the powerful and manipulative Medici banking family and its head, the legendary patron of the arts Lorenzo d’Medici (1449-1492) known as “Lorenzo the Magnificent.”

After honing his talents and being exposed to a wide range of artists and intellectuals as a member of Verrocchio’s workshop, at the age of twenty Leonardo joined the artist’s and doctors association, the Guild of St. Luke.  After surviving a sexual scandal and completing some commissions for altarpieces in Florence during the first decade of his professional career, Lorenzo de Medici sent the young artist along with a silver lyre he had made as a peace-making present to Milan’s iron-willed ruler Lodovico de Sforza (1452-1508), the powerful Duke of Milan who was known colloquially as “il Moro” or “the Moor” for his dark complexion and perhaps even darker soul.  The text of the letter Leonardo wrote Lodovico de Sforza offering his services advertised his manifold talents with his artistic ability mentioned only as an afterthought.

Leonardo’s Lady with Ermine

Leonardo in Milano 

By traveling from Florence to Milan Leonardo had been transferred from the payroll of one Renaissance Prince to another.  Once in the employ of Sforza – for a demeaning wage – Leonardo was tasked with a number of less prestigious projects, which included mundane but difficult tasks for the Duke’s household. He worked on costume and stage designs for the Duke’s lavish parties, architectural schemes, war machines, as well as designs for floats and pageants. Meanwhile, in his spare hours he explored the natural world and the sciences and came up with fanciful inventions, writing and page after page of stunningly illustrated notes.  Written in reverse, Leonardo’s notebooks would be seen by only a few viewers for hundreds of years.

Finally, in a struggle for relevance and an appeal to his master’s vanity, he offered to sculpt a monumental bronze horse known as the “Gran Cavallo” which was to be a monument to Francesco Sforza (1401-1466), Lodovico Sforza’s predecessor.  The subject of running horses had long interested him and he liked the challenge of casting a bronze on an unprecedented scale.  However, like many of Leonardo’s other plans, the production of the horse, which was actually modeled in clay to great acclaim, dragged on for years and was never completed. Eventually, the seventy tons of bronze that were to have been dedicated to the casting were later used to make canons when the French threatened Milan.

The Commission for the Last Supper 

About 1492 or 1493 – earlier than had been previously thought – Leonardo received a commission to paint a mural of the Last Supper on the wall of the refectory at Milan’s Santa Maria delle Grazie monastery.  This work was to be paid for by his patron Francesco Sforza, the Duke of Milan.  There does not seem to be any hard evidence as to whether Leonardo came up with the idea of painting a fresco in the refectory in an entrepreneurial fashion and proposed it to the Duke, or if the church fathers wanted a fresco and selected Leonardo as the painter.  Since the final product featured the coat of arm of the Sforzas, it was probably one of the commissions that “Il Moro” made in order to enhance his reputation and affirm his position and prestige as the ruler of Milan.  Because the first preparatory and compositional sketches date to about 1492, the project may have been one Leonardo sought.  As the artist had an expensive household to support and was always short of funds, the commission for the Last Supper must have been a welcome one.  Because the refectory was used for meals, the subject of the “Last Supper” was an ideal subject for its  location.

Any large wall painting is an ambitious undertaking and if we can step into the sandals of the artist for a moment, we can see that while it can be a triumph for the painter and his studio, it can also be an embarrassment, for a poorly executed fresco – especially one on a wall almost thirty feet wide, is there for all to see.  Failure as well as success is there for posterity.  So, this undertaking would have one that Leonardo would have taken on with a mixture of excitement and trepidation, for while he felt he was up to the task, he had not attempted something so ambitious before and he did not have the large workshop that successful fresco painters usually relied upon.

Other Last Suppers

By the time Leonardo began to work on sketches for his Last Supper, the subject had already become an artistic convention in the Early Renaissance.  He would have seen a number of Last Supper frescos around Florence, where he grew up and received his training at Verrochio’s workshop.  First of all, there is the beautiful Cenacolo di Santa Croce by Taddeo Gaddi (c. 1300-1366) which was painted about 1340, just a few years before the Black Death made its ghastly visitation on Florence in 1348.  Then, there is the Cenacolo di Santa Apollina by Andrea del Castagno (c. 1421-1457).  This bold fresco with the apostles depicted in a luxurious dining room must have had a marked effect on the young Leonardo.

The Fabled Composition 

A complex composition where there are a number of figures interacting with each other is the most challenging subject for an artist to paint.  Just like in the sports of diving or gymnastics, there is a degree of difficulty in art.  The human figure is a difficult enough prospect, but as you multiply the number of figures – and of course there are thirteen of them in the “Last Supper”  – each of who must relate first to each other and then also work as a clear and cohesive whole, the scale of difficulty is on an entirely higher plane.  This overall scheme is called the “composition” and in a large fresco it is everything.  For no matter how beautifully each of the individual figures is rendered, if the composition isn’t pleasing the battle is lost.

Leonardo’s Painting Technique for the Last Supper

Now, there is no doubt that Leonardo would have been familiar with the true or buon fresco (“good fresco”) technique that was traditionally used for wall paintings, even though he had not worked on frescos as a member of Verrocchio’s studio. After all, the greatest works of fresco painting surrounded him in the churches and cathedrals of Florence when he apprenticed there. The buon fresco technique is highly regimented, requiring a great deal of planning and steady, painstaking day-by-day work as the pigment can only be applied to damp plaster and major corrections require actually cutting a piece out of the wall and then re-plastering it.  Now, if we know anything about Leonardo, it is that he would have been temperamentally unsuited for doing a large wall in the buon fresco technique. I have long felt that Leonardo was the prototypical man with ADD – Attention Deficit Disorder – and so I feel he would never had the patience to see the project through under the limitations of buon fresco method, one he didn’t have experience in in any case.

Instead, of being limited to working on his wall only when a fresh coat of plaster had just been smoothed onto the wall, Leonardo chose to work in his own adaptation of the Fresco Secco (“second fresco”) technique where paint is applied to a dry plaster wall.  Leonardo would have realized that the secco technique was less stable than true fresco, for as he came of age in Florence he would have already seen the deterioration of the over-painting done by earlier masters who sometimes used fresco secco over buono frescos to make additions and add colors they could not use when the plaster was wet.  Apparently Leonardo had faith in his ability to create his own adaptations of medium that would overcome the limitations of the secco technique and allow him to paint his “Last Supper” according to his own internal schedule.

Now, Leonardo knew that he had to have a dry ground, a dry surface to paint on and any fool could see – and smell – that the walls of the refectory were left damp after it was lashed with rain.  So, after he was said to have sealed the wall from moisture with “pitch” which is simply the tar that oozes out of the ground and has been used as a waterproof sealant for centuries and mastic, which is a resin that comes from the Greek mastic tree which has also been used as a sealant since classical times, he and his assistants laid on a layer of gesso as a ground for the pigment layer. Gesso, is the Italian word for “chalk” and in artistic use chalk was mixed with animal-skin glue in order to create a sticky mixture that when dry would provide a white ground that would have enough “tooth” for the paint to stick to.  Then, once Leonardo – or most likely his assistants under his supervision – had finished preparing the surface of the wall, it was ready for the critical step of transferring the composition to the wall.

For his adaptation of buon fresco Leonardo intended to us a mixture of tempera – where the ground pigment is suspended or carried in a mixture of water and egg yolk – and oil paint where the medium of oil – apparently walnut oil – would carry the pigment.  Chemical analysis has revealed that both tempera which is a water soluble medium and oil paint which is not water soluble, were used on the Last Supper but exactly how he layered and utilized these two mediums will never be known because of the deterioration of the mural and the subsequent restorations and over-painting. Recreating his process after five-hundred years  – even for the specialist – is a matter of some conjecture and speculation. This commentator, a non-specialist, feels the finished work may have looked more like an oil painting with an enhanced feeling of depth and dimensionality when the painting was finished and that Leonardo used oil paints – which was a medium that was then a new medium in Italy – because he could achieve an appearance that was not possible with tempera alone.  We have to recall that viewers of the time felt it was an inspired, revolutionary, work and I feel that his use of an oil emulsification was done to achieve a more lifelike final product.

The hall that Leonardo was commissioned to paint a mural for was not the most hospitable environment for what was soon acclaimed to be a landmark work of art. While Leonardo’s attempt to seal the wall with the tar and mastic shows that he was aware that the damp building presented problems – especially for his adaptation of the dry or “secco fresco” technique that he intended to use – he probably didn’t understand the severity of the problem until he was well along with the process of painting it.  You see, Milan is lashed with wind, rain and snow that comes out of the Italian Alps that serve as the dramatic backdrop for the city. And, the wall that Leonardo was commissioned to paint his “Last Supper” on faces north, so it receives the full brunt of the chill winds and rains of the wetter seasons.  Masonry construction is subject to settling over time and it moves, just as the earth gradually shifts and moves, so it is  almost like a living, breathing thing. Despite the brick and mortar walls and the stucco that protects the outside and the smooth plaster on the interior wall, some moisture still passed through. So, in the refectory where the “Last Supper” is sited, the winter damp still seeped through the organic materials used in its construction. During the hot, humid summer, the wall where Leonardo’s masterpiece is sited would weep with moisture from the muggy climate as well as the underground river that runs beneath the builduing. In a sense, the walls breathe, inhaling and exhaling with the seasons and climatic conditions.

When a conservator describes a painting as “unstable” it is usually because there is a problem with the ground layer the artist has applied.  No matter what surface – know to art restorers as a “support” – an artist chooses to paint on, that surface needs to be properly prepared in order for the paint or “pigment layer” to adhere properly to the surface.  This is the case whether an artist paints on a wooden panel as many Renaissance painters did, on a canvas as most painters do today, or on a wall. The exception to this rule is the one we have already noted, the traditional old fresco technique, buon fresco which is unique in that as part of a chemical reaction, the pigment actually becomes part of the masonry wall, not simply something that is painted on a ground layer applied to the wall.  So, if something is wrong with the ground layer, the wrong mix of materials for example or if it fails to stick to the support, chances are that anything painted on top of that ground is not going to adhere as well as it should, causing instability which will usually mean a flaking or a cracking paint layer.  If moisture works its may through to the pigment layer, the work of art is going to be at risk whether the medium was a water soluble paint or the pigment was mixed with oil.  Moisture is an insidious enemy and Leonardo, like every trained painter realized this. So, in order to provide a moisture barrier to protect the pigments that he was going to apply, as we have seen, Leonardo is said to have used pitch and mastic– to seal the wall and protect the painting.

An older theory is that ironically, in order to protect his painting from moisture, the materials that Leonardo are said to have used to seal the wall may have done their job too well.  Before he applied the sealants, the wall could “breathe.”  The moisture that built up in the masonry of the wall during the wet season would gradually dry out during Milan’s hotter weather.  However, by waterproofing the wall well enough to use his innovative medium, Leonardo may have sealed the condensation up in the north wall and trapped it beneath his precious painting.  Then, the always-damp wall became the perfect environment for the little microorganisms that we call mold. I think it is safe to assume that poor Leonardo was already fighting issues with the moisture and mold before the painting was even finished.

The Decline of the Last Supper 

Soon after the mural was completed the French invaded Milan and imprisoned the Duke, il moro.  Leonardo had to pack up and flee and as he set out for Venice, one would guess he might have been relived to leave Milan for The Last Supper was probably already experiencing some deterioration.  As technically proficient as he was, he may have realized that he was already fighting a losing battle with the weeping wall while he was still at work on the painting.  Perhaps some of the delays that drove the Duke and the Prior to distraction and Leonardo’s long hours of consideration and consternation in the course of his work were due to his worries about the instability of his painting.  My guess is that the painter was relieved by the advance of the French as it let him off the hook with a powerful patron.

Perhaps the problems that plagued the painting as it aged were not too severe during Leonardo’s lifetime because the earliest copies by Marco d’Oggiono (the best one of which was destroyed during World War II), which were done early in the 16th century, do not show evidence of deterioration. However, if there were already significant organic growth, it would have been only necessary for d’Oggiono (c. 1470-1539) to wipe the mold away to see Leonardo’s work. However,  later copyists were working from a disintegrating work and therefore, their works would have been more interpretive. Antonio De Beatis, the secretary of the Duke of Aragon viewed the Last Supper in 1517 and wrote in his published travel diaries that “already it begins to spoil.” Certainly, within a few decades of Leonardo’s death the problem of the moisture seeping though the walls caused the paint that Leonardo had painstakingly applied to flake off and the damp wall and it had become a artistic habitat for microorganisms.

In 1550, just a few decades after Leonardo died in France, while in the employ of the French King, Vasari, the artist and pioneering art historian was already describing the “Last Supper” as “ruined” and a “mass of confusion.” The colors had probably disappeared under a greenish haze of microscopic vegetation.  Apparently, the weeping wall would be wiped down periodically, which would not be the best thing for the paint layer, which was already loosing its adhesion.  Late in the sixteenth, century Giampaolo Lomazzo (1538-1600), the mannerist painter and art writer, blamed Leonardo for the deterioration because of his use of oil-based pigments on a improper ground layer.  His account also described the painting as “ruined.”  In spite of his criticisms, Lomazzo described a work “that was one of the marvelous works of painting ever made at any time by any painter in oil” and from his vantage point in the sixteenth century he would have been able to see most of the masterpieces of the Renaissance in their original condition. He also made at least one copy of the Last Supper for the convent at Castellazzo which has been lost.

Cardinal Federico Borromeo (1564-1631), the Archbishop of Milan, who had humanist sympathies, was so concerned about the deteriorating condition of the “Last Supper” that he commissioned a copy of it from Andrea Bianchi (active c.1612-1640), known as “Il Vespino” in 1612 in order to preserve its memory for posterity’s sake.  Then in 1635, Don Ambrogio Mazenta wrote that “this precious ideal was ruined because it was painted in oil on a damp wall.” To add insult to injury, in 1652 a taller doorway was cut into the wall beneath the painting, intruding into the lowest section of Leonardo’s painting, obliterating Christ’s feet and distracting the viewer’s eye from the composition the painter wanted them to see.

In the 1670s, yet two more accounts of the Last Supper’s deterioration were recorded.  In 1672 Pietro Paolo Bosca assiduously observed that the refectory’s humid interior was responsible for the painting’s decline.  Perhaps the most poetic description of the declide of the masterpiece was penned by Carlo Torre who compared the Last Supper to “a sun in the last hours of the day, whose falling rays, if they do not appear resplendent, at least give notice of having been the brightest; one still sees vivid expressions, boldly foreshortened figures, resplendent colors, and marvelously well-drawn poses.

Failed Attempts at Restoration 

In spite of the terrible state of “The Last Supper,” apparently a major recovery effort was not attempted until 1726, more than two hundred years after Leonardo painted it, though there was some discussion of an unrecorded attempt at cleaning the painting in the 1650s.  Now, the art restorers of previous generations did not set out to “conserve” what was there, but to create a semblance of what they thought the painting should look like. Until recent centuries, restoration was more of a sideline for unsuccessful painters than a professional career.  The men who worked on Leonardo’s wall sought to give viewers what they came to see… a “Last Supper” and we must keep in mind how the painting was seen at that time – as an object of religious veneration rather than the way we see it today – as a cultural treasure.  So, the first restorer Michelangelo Bellotti, a minor Milanese Baroque painter, tried to clean off the mold and grime – apparently with soda or caustic potash – and then repainted the missing sections with very opaque applications of oil paints.  Some thought that he went too far and that now the Last Supper almost looked like a fresh painting.  When finished, Bellotti sealed his work and what was left of Leonardo’s with varnish.

Because of the inherent instability of the ground the “Last Supper” was painted on and the moisture issue, the painting would have kept growing moldy and both what was left of the original pigment layer and the repainting would have deteriorated again.  In 1770, Giuseppe Mazza (1653-1741), a Bolgnese sculptor, was hired to do another restoration.  He started by cleaning much of away his predecessor’s work and began to paint over the vestiges of Leonardo’s work until his over-painting of the heads caused such controversy among the Milanese, that it was halted before it could be completed on all the figures.

During the Napoleonic age there was a new found interest and respect for the works of the Renaissance. This was part of the Neo-Classical Age’s reverence for the past.  In 1796 after occupying Lombardy and turning the Dominicans out of the monastery, the anti-clerical French actually used the refectory to lodge troops until Napoleon himself came to see the painting.  France’s Le Premier Citoyen left orders that Leonardo’s Last Supper should be protected from harm.  At that time the French removed Leonardo’s manuscripts from Milan, which were used by Giovan Battista Venturi (1746-1822) to write his landmark work on Leonardo’s work in physical science and mathematics.

Unfortunately, Napoleon’s wishes were not honored and the French troops used the refectory to house wares and hay, damaging the Last Supper still further and the troops apparently even vandalized the painting. Finally, after many complaints, the doors to the refectory were walled up in an effort to protect the damaged painting.  The Neo-Classical painter Andrea Appiani (1754-1818) sent First Consul Napoleon a report on the Last Supper that stated, that “the slightest bump causes precious fragments to rain down.” In his sympathetic and far-sighted appeal he, for the first time addressed many of the issues surrounding the painting, including the humidity inside the refectory, protecting it from too many visitors, defending the location “from the ravages of time” and creating surroundings worthy of the painting.

Soon after, Appiani was authorized to find someone to restore the work “for the glory of the nation” and he commissioned Giuseppe Appiani of Monza to make the effort, but it is not clear how much he achieved.  Instead, the efforts of Giuseppe Bossi (1777-1815) who was commissioned to create a full-sized “cartoon” of the Last Supper took precedence over conservation.  Bossi was charged with creating a copy of the tragic masterpiece so that the Italian artist Giacomo Raffaelli (1753-1836) could create a mosaic version for Eugene Beauharnais (1781-1824), Josephine’s Nephew and the new Viceroy of the Kingdom of Italy.  Bossi replaced the unstable wall under the bottom of Leonardo’s composition, walled up windows, constructed scaffolding and probably overheated the room.  Through his artistic and collaborative efforrts, the artist thought he could re-create Leonardo’s lost original painting.   He did extensive tracings of the figures, placing his paper directly on the fresco.  While these drawings they give us an idea what the painting looked like at the time, the process of doing them was unnecessary and intrusive. While Bossi wrote the first book on the Last Supper, (Del Cenacolo di Leonardo da Vinci Libri Quattro) and helped to fuel a much greater interest in Leonardo, the mosaic project was properly criticized for being a rigid and bloodless Neo-Classical interpretation of the original that relied too heavily on copies of the Last Supper.

Milan’s Accademia di Brera (f. 1801) of which Bossi served as secretary, next became responsible for the preservation of the Last Supper.  After the long years of the Napoleonic wars, the Austrians now  controlled Milan.  Bossi’s successor at the Accademia, Giuseppe Zanoja next  led the efforts to finally do something about the condition of the painting.  With the Austrians in charge, the fate of the Last Supper was the subject of commission, research and ill-fated experimentation.  In 1821, a painter-restorer named Stefano Barezzi came up with a plan to actually remove the painting from the wall it was painted on, something he had apparently done successfully to frescos in the past. In Venice, where humidity causes problems even with conventional frescos, the “Strappo” method was developed to safely remove the fragile works of art from the walls they were painted on. Before Barezzi got to work, another pair of restorers Antonio de Antoni and Franceso Fidanza Barezzi, were ordered to clean part of the painting and they attempted to use water, only learning that the portion they were trying to clean was tempera and so, incredibly, they washed away most of the pigment on two heads in the process. Whether what they destroyed was Leonardo’s work or a later over-painting may not be clear, but the assumption today is that the heads they damaged, were those of Judas and St. Peter, where the pigment is now almost entirely missing.  Unfortunately, that was not the end of the sad episode.  Barezzi did further damage trying to remove the section of the Fresco he did work on.  Fortunately, he was not allowed to work on the figures and most of his damage was confined to the table below Christ.

The 1850’s were a time of great activity in the historic refectory.  Incredibly, Barezzi was still actively restoring paintings and he again won a commission from the Accademia to work on “consolidating” the paint on Leonardo’s wall.  This time he also cleaned the lunettes bearing the Sforza’s coat of arms, wiping away the whitewash that had covered them for many years.  In 1856 the Austrians, who still ruled Milan, began considering restoring the refectory itself.   The building finally received a sympathetic restoration by Giuseppe Knoeller in 1872, the same year Pietro Magni’s civic sculpture of Leonardo was unveiled in the Piazza della Scala in Milan.

The 20th Century Last Supper 

At the turn of the 20th century it was decided that once again the “Last Supper” needed restoration.  I have a sneaking suspicion that the motivation for this attempt was at least in part because the Milan World’s Fair was scheduled for 1908 and that then, as now, these municipal coming out parties mean that civic leaders want to scrub their metropolis clean and make everything beautiful for the tourists who they hope will flock to their city.  Italy was now unified and so the Leonardo authority and architect Luca Beltrami, the first director of the Ufficio Regionale per ka Conservazione dei Monumenti began the process of restoring some of Milano’s cultural monuments including the Castello Sforza. So, a Milanese painter and restorer named Luigi Cavenaghi (1844-1918) was engaged to restore Leonardo’s masterpiece once more.

Now, Luigi Cavenaghi is one of the few heroes in the long, sad story of early art restoration.  He was the protégé of the important art restorer named Giuseppe Molteni and together they developed a much more sympathetic concept of restoration or, in their skilled hands, “conservation.”  Where earlier restorers would often take paintings removed from damaged frescoes or larger works and add to them or repaint them as to make them more marketable, these men brought the terms “authenticity,” “integrity” and “originality” to their craft, stripping away voluntary over-painting and guarding against overzealous cleaning.

Instead of getting right to work, after he started in 1903, Cavenaghi took a number of months to make an extensive photographic study of the painting.  With the Last Supper, even the photographic evidence can lie as many photographers retouched their images to improve what their negatives revealed! The good restorer concluded that the medium Leonardo had used was mainly egg tempera, not overwhelmingly an oil medium as previous restorers had concluded. Cavenaghi then began to carefully clean away the organic material and the results of botched attempts at restoration and to “consolidate” the surface which means making sure what pigment was left adhered to the surface of the wall. He cleared away some of the adhesives used by previous restorers and consolidated what remained of the painting. Unfortunately, the resins he used to try to keep the original pigment layer intact had the opposite effect and even more was lost when they dried out.  He also left a lot of the historic over-painting on the wall as he concluded that there was little of Leonardo’s work underneath it.

Another restorer named Oreste Silvestri (1858-1936) began working on the painting in 1924. Unfortunately, in the long run his work was terribly destructive. He furthered the work of cleaning off old in-painting and varnishes and consolidating what was left, but he used resin-based fixatives to fill the cracks in the wall and then used some of the same material on the colors, perhaps in an attempt to seal the paintings in a method similar to the way the ancient Romans did. Then, incredibly, he used hot rollers in an effort to smooth out blistering paint and in the course of this procedure more pigment was thought to have been lost. Under the fascist government of the 1930s, more inspections were carried out, discovering that there were large stains caused by the humidity and a generally rough surface where the paint layer was separating from the imprimatura.  At the very time these upsetting discoveries were being made, Milan was honoring Leonardo with a large loan exhibition with works from all over the world.

When World War II broke out, the young Italian nation had thrown its lot in with Germany and the Axis powers.  This put the industrial heart of Milan in the cross hairs of Allied bombers and put Santa Maria delle Grazie at enormous risk.  In attempt to protect the “Last Supper,” the north wall of the refectory was sandbagged and braced.  On the August 15, 1943, Milan was bombed and the refectory suffered a direct hit and the vault and one wall were reduced to rubble.  Fortunately, the “Last Supper” survived but the masonry wall it was painted on was shaken by the blast, undoubtedly causing still further cracking in the surface of the wall and without the protection of a building around it, for a number of months, the “Last Supper” was only protected by a tarpaulin.  Afterward all this the humidity inside the building only increased and the surface of the painting almost turned to powder.

All of these twentieth century efforts to stabilize, clean and recover what was left of Leonardo’s troubled masterpiece continued after World War II.  In 1947  Mauro Pelliccioli, Italy’s most famous art restorer, was hired to work on the “Last Supper” under the eye of Fernanda Wittgens, Milan’s Museum Director. This attempt was heralded by Italian authorities as “the greatest undertaking ever accomplished in the art and science of restoration. Pelliccioli claimed that Leonardo’s work “had been ruined by a bunch of morons.” Under the constant attention of curious tourists, the irascible old restorer decided that the glue that had been used in previous attempts to consolidate the painting – to make it adhere better to its ground layer – had failed because the moisture was interfering with the water-soluble glue.  So between 1947 and 1949 the restoration team used shellac in an attempt to get what was left of Leonardo’s pigment to stick the ground the artist had applied.

Between 1952 and 1954 Pelliccioli worked to clean the fresco again which lightened up the dark tonalities that the now-discolored over-painting and applications of varnishes had caused. Using a solution thought to be diluted turpentine he worked on the faces, perhaps losing more of Leonardo’s original pigment layer in the process, but after his efforts, the faces were lighter.  He claimed that the work required him simply “to scratch until you reach the real Leonardo.”  So, using a photograph of the 1520 copy by Andrea Solari (1460-1524), which had been destroyed in the war, and his memory of its colors as a guide, that is what he did.  However, once again, Pelliccioli choose not to remove all of the all-too-generous over-painting on the “Last Supper” even though he estimated that only  30% of Leonardo’s work survived underneath.

After working on the painting each new restorer seemed to realize that the generations of viewer’s who had come to love Leonardo’s work as a cultural icon really had little idea of what Leonardo’s original painting looked like.  The painting that the world loved from their visits to Milan or from photographic reproductions on prints and post-cards was in reality only Leonardo’s brilliant and unique compositional scheme with his figures over-painted by one restorer after another from the Baroque Era to the 20th Century.

Because the conditions that contributed to the deterioration of the painting and the growth of organic material on its surface had never been addressed, let alone arrested, the “Last Supper” was once again a fuzzy mess by the 1970s.  A microscopic look at the surface would not reveal the smooth surface that would be seen with a fresco that was in proper condition, but something resembling a lunar landscape.  Mold, glues and adhesives and residue from previous vanishings had coated the surface of the painting and the cracks that ran across its surface. The shell-shocked surface of the painting was covered with the brown film of smog, that 20th century addition to the witches’ brew that threatened the painting.  Leonardo’s original white ground was detached in many places, as was much of what was left of what remained of the original pigment the artist had applied.  Not only was the appearance of the painting a mess, but experts came to the conclusion that what remained of the old restorations and cleanings was actually adding to the deterioration of the painting, so once again, the cry went up that “something has to be done to save the “Last Supper.”

The Latest Restoration of the Last Supper

The restoration of a world-renowned masterpiece like Leonardo’s “Last Supper” is not one that is taken lightly.  In fact, the very thought of someone working on a masterpiece fills curators and superintendents with dread.  No one wants to be the one responsible for damaging an irreplaceable and iconic work of art.  This means that the notion of undertaking the conservation of a masterwork like the “Mona Lisa” isn’t be considered until it is more than necessary, for everyone involved knows a cleaning will alter the somewhat foggy, obscured look of a Renaissance work millions of viewers have gotten used to, but the painting viewers are used to may bear little resemblance to what the artist actually painted.

The outcry over the radically more colorful look of the Sistine Chapel after years of conservation was enormous and no curator or museum director has forgotten the fall-out. So, the stabilization and restoration of the “Last Supper” was only started decades after it was necessary, after its deterioration had become a tragedy to art lovers all over the world.  Fortunately, this latest attempt at conservation has occurred after the technological developments had made analyzing the state of the painting and separating what Leonardo did from the restorer’s work at least a possibility.

The restoration of Leonardo’s “Last Supper” was overseen by Pietro Marani, Director of the Pinacoteca di Brera in Milan and Pinin Brambilla Barcilon who led the team of restorers.  Modern Italian restorers have the reputation for being more temperate and sensitive then their American and British counterparts, so they prefer to work slowly and try first and foremost to “do no harm” to what the original artist had laid down on panel or wall.  In the case of the “Last Supper” the damage had already been done and so the effort overseen by Signora Brambilla would be to stop further degradation of the masterpiece and to discover what remained of Leonardo’s original work beneath all the subsequent over-painting and re-varnishings.

From the beginning, those in charge of the restoration of the “Last Supper” knew that the entire effort would have been a complete waste of time and enormous sums of money had they left the environment that the painting was in the same.  After all, it was the unique environment that had given Leonardo such headaches and caused the rapid deterioration of his great composition.  So, the first issue was to create a museum-like environment where the masterpiece could remain stable.  One major problem that most of us don’t consider when we think about the maintenance of a work of art is us, for the art aficionados who appreciate a work of art can love it to death.  The moisture we bring into a closed environment like a refectory or chapel on our shoes and clothing during inclement weather can damage the painting.  Then, the dust and dirt we carry on us during the dry season can cause other issues.  Even the moisture of our breath and the sweat of our bodies is an issue when tens of thousands of visitors view a painting like Leonardo’s Last Supper in a closed enviornment each year.

In order to combat the original problems that the damp refectory presented and the issue of how thousands of visitors affect the painting, a sophisticated air filtration system was designed and developed in order to remove excess moisture from the environment and to control dust and dirt.  A barrier was developed that would wick moisture from viewer’s shoes and keep Milan’s dust and pollution away from the painting.  Then, the climate inside the refectory was controlled so that the heat and humidity stay at consistent levels rather than changing dramatically with the seasons, as they had for the painting’s first half-millennium. Finally, the number of visitors who can see the painting and the length of time they can stay would be strictly regulated so that the number of viewers won’t damage what remains of Leonardo’s work. Once the environment was made more stable, the restorers felt that once it was restored, the “Last Supper” would be able to survive in perpetuity.

The first step in the actual conservation of the “Last Supper” was to document  what the state of the painting actually was.  Fortunately, modern conservators have a battery of  technology at their disposal and everything in their quiver was thrown at Leonardo’s painting.  The structure of the masonry wall the painting is on was subjected to sonar and radar analysis and probes cameras were inserted into the wall to check its stability. The painting was x-rayed and exposed to infrared light in an effort to see what remained underneath the zealous over-painting.  Minute core samples were drilled and analyzed in laboratories.  Microscopes were utilized to view every inch of the painting’s surface.  Then, extensive new photographs were taken and comparisons made to photographs that had been taken in previous decades to reveal valuable clues.  The cracks that are now on the painting were mapped so that a plan could be developed to arrest their progress.  Extensive chemical testing was done as the samples could reveal properties that would enable the conservators to determine what paint and varnish was from which of the previous restorations.

The actual conservation meant a painstaking process of dipping small Japanese mulberry paper squares in solvent and then wiping away the over-painting previous restorers had done.  Because the conservator’s research had confirmed that the work of previous restorers was not only obscuring what remained of Leonardo’s work but actually degrading it, for the first time, they resolved to remove every trace of old over-painting for the first time.  When the conservators found stubborn areas where the old pigment or fixatives could not be massaged gently away with the mulberry squares, brushes and other implements were used. The pace of Signora Brambilla’s restoration can only be described as glacial. They were often only able to clean an area the size of a postage stamp in a full day’s work.

As the modern restorers worked on Leonardo’s wall, they  uncovered what chemical analysis showed them was left of Leonardo’s original pigment layer that previous restorers had over-painted.  There were highlights on the draperies behind the figures and in the shadows of the windows, some the master’s walnut oil bound blue pigments survived.  Traces of the Flemish-patterned draperies that lined the walls behind the disciple’s tables can now be seen, confirming that the Royal Academy’s historic copy of the “Last Supper” by Giampetrio (1495-1549) was indeed accurate. Once the sealants and varnishes of past restorations were removed, Brambilla and her team discovered that what was left of the original pigment was quite subdued in color, indicating that Leonardo may have used almost transparent oil glazes or varnishes (traces of which may have been removed by later restorations) to give the completed mural a deeper, richer look.  As any of us with experience with oil based pigments understand, glazes are often what gives a painting its depth and luminosity.  We can only guess at what The Last Supper looked like when it was fresh.

So, once she had cleaned away the results of one botched restoration after another, Signora Brambilla is said to have found that only about thirty percent of what Leonardo had painted remained intact on the wall.  Now, whether this thirty percent refers to the total surface area with some trace of Leonardo’s pigment layer or the total amount of the paint he applied in layers that is left isn’t clear.  In any event, the Signora found that only faint trace’s of the master’s hand remained in some places. Unfortunately, in her own excellent account of the story of the Last Supper and the  restoration she overstates her success.  For example, she claims that “We can grasp the love, sorrow, obstinacy, hate and guilt on the apostle’s faces, until now reduced to mere caricatures.”  With so much pigment missing and with the probability that transparent glazes and subtle modeling that flaked away and was skinned off in all-conceived restoration attempts, it seems like a tall order to claim that now this attempt had revealed the true Leonardo. The many missing areas created a dilemma for the conservator. Would her “restoration” be considered a success to Milan’s throng’s of visitors if they came into the refectory and saw that after years of painstaking work, all that was left was thirteen shadowy, faded, fragmentary figures lacking even the cohesion that had been provided by the unfortunate old over-painting? Or, should she attempt to do the same thing that all the other restorers had done in her place and try to in-paint the missing areas, in an attempt to give some fidelity to the legendary work?

Well, as we now know, Signora Brambilla decided to go down the same well-trod past as restorers past have done. This would be a very controversial decision, but she knew that every critical decision she made on the project would be, but she was sure of her course.  So, with the old copies as her guide, she attempted to replicate the missing portions of the figures as best she could, to give them some body and to unify the whole. She chose to work in watercolor so that the process would be reversible. Then, in order for her work to remain distinct, she chose to in-paint in colors that would be complementary but remain distinct from what remained of the master’s pigments.  Of course, she was Singora Brambilla, not Maestro Leonardo, so while her painting gives us some concept of what “The Last Supper” once looked like, it cannot have the power or the grace of the original that disappeared some five hundred years ago.

The Controversy

Now, the term restoration or “conservation” which is the term preferred by professionals today seems harmless enough, but in truth removing the dirt and grime and organic material of five hundred years requires strong medicine, which actually means powerful solvents. Old in-painting actually has to be dissolved and wiped away.  Conservation is as much an art as a science and while the level of difficulty of cleaning discolored varnish and a thick layer of dirt and pollution from the surface of a masterpiece is difficult enough, the task of discerning exactly what was Leonardo’s original work, which was apparently rendered in a mixture of techniques, using both egg as a binder and possibly walnut oil must have been an incredible challenge. Critics wanted to know if it was really, truly possible to use powerful solvents to remove the old over-painting while not damaging what was left of the master’s pigments underneath? And, the truth is that only those intimately involved in the project really know what was salvaged and what may have been lost in the process.

What did the “Last Supper” actually look like when it was unveiled and viewers were so astonished at its quality and originality?  Some of the issues that come to mind from this viewer would revolve around what we call glazes in oil or what someone working in the technique of secco fresco would call “l’ultimi mano” or “the final layer.” We know that when he worked in oil, Leonardo made masterful use of its depth and luminosity. As a young apprentice, he added an exquisite oil passage of an angel to his master Verrocchio’s tempera painting “The Baptism of Christ” (1474-75).  Once he decided not to use the traditional fresco method, would he not have taken full advantage of the fact that when using pigments suspended in oil for some passages he could paint in almost transparent layers or “glazes?” When artists use very small amounts of pigment suspended in varnish or oil to add depth and luminosity to their work, it is called a “glaze” and it is very difficult for a restorer to discern how deeply he or she can clean. What appears to be a discolored varnish may actually be a filmy glaze and if a glaze layer is removed improperly the painting won’t look the same. Glazes of that “l’ultimi mano” often unify a painting.  The wonderful warmth in the skin tones of Leonardo’s “Lady with Ermine” was built up with layer after layer of greatly thinned pigment. In many of the great master Leonardo’s work each almost imperceptible layer is critical to the painting’s overall effect.   So, did the latest team of restorers manage to bring what was left of Leonardo’s work back to life without losing any of the effects he may have used?

The late Professor James Beck was a scathing critic of many attempts to restore masterpieces and he became so intense a critic that he and Michael Daley, a British art critic formed an organization to monitor such efforts called Art Watch International. Of Brambilla’s work Beck said “This woman has simply produced a new Brambilla.  What you have is a modern repainting of a work that was poorly conserved.  It doesn’t even have an echo of the past.  At least the older over-paintings were guided by Leonardo’s work.”  He was particularly scathing in her attempt to fill in Christ’s head where little of Leonardo’s pigment remained.  “It looks silly.  The mouth is peculiar and off-center.”  Daley, his partner in Art Watch wrote that “The restoration has cut the painting’s link with the past, reducing it to little more than a naked wall.”  His overall view was that the restoration was “simply catastrophic.”  Professor Martin Kemp of Oxford, who has made Leonardo his life work, was more measured, but he questioned Brambilla’s decision to paint in the missing areas and said that “In the Last Supper, the amount of original work by Leonardo is very small.”

There was no doubt that Signora Brambilla also had her defenders, especially in Italy. Many viewers felt that the painting was “more readable.” The Australian Art Historian Lorenzo Matteoli, clearly an enthusiast of high technology, has an interesting perspective. He feels that by by freeing the painting of the over-painting what is left can be analyzed with graphic software in an effort to eventually recreate what was once there.  Giulio Bora, the Italian Renaissance historian stated that “No one could have worked better than Brambilla.  After all, they have been trying to save the Last Supper since the mid-1500s.  The restorer defended her work by pointing out that they had discovered passages of Leonardo’s work that had been covered for centuries “Take Matthew.  We always knew him with dark hair, yet we discovered he was blond.”  She also cited the fact that many details on the table emerged virtually unscathed after her efforts.  In an essay the Australian restorer Matteoli claimed that the painting “has the luminosity and highlights that must have left viewers in awe five centuries ago.”

So, which side is correct, those who feel as the late Professor Beck did – that a great work of art that is deteriorating be allowed to die a “graceful death” rather than be “murdered” by overzealous restoration?  Or, those who would use the latest technology to assess the state of a masterpiece and then to carefully attempt to keep it from deteriorating further, working sympathetically to try to stay true to the artist’s original intent?  Is it possible to split the difference, to work hard to do no harm first, to preserve something without attempting to “restore” it?  These are some of the questions presented by the long and troubled history of Leonardo’s “Last Supper.”

After x-rays we know that Leonardo’s “Mona Lisa” has very little drawing, the figure was built up one almost imperceptibly brushed layer after another, which is probably why Leonardo is said to have worked on it for years.  While it may be difficult for a non-artist or someone unfamiliar with academic practice to understand, the Mona Lisa may be best understood as a tonal painting, where the relative values have been used to build up the figure rather than a linear under-drawing. Could he have tried something similar on The Last Supper?  Because of the problematic nature of the technique he used for the “Last Supper” and its subsequent deterioration, we can only be haunted by imagining what the painting looked like when it was fresh and painted to the master’s satisfaction


Today, when we go to visit the Leonardo’s monumental “Last Supper” in Milan, I think it’s best to try to look at the painting as contemporary viewers would have seen it five-hundred years ago, as a great object of religious devotion for the faithful. It is masterpiece that tells an all-too-human story of faith and betrayal.  One does not have to be a Christian or even a religious believer for the painting to “speak” to them.  We can all imagine Jesus as a man who is compelled to follow through on the terrible fate that he knows awaits him.  Virtually every one of us has experienced some form of betrayal and, so we can understand the well of emotion felt by Christ as he reveals that he will be betrayed by one of the very disciples sharing the meal with him.  And, as humans we can understand the sense of bewilderment felt by eleven of them as they wonder which one of their number will betray their master…

Copyright 2009-2011, Jeffrey Morseburg, not to be reproduced without the specific written permission of the author.


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