In 1495, Leonardo da Vinci stood on a wooden scaffold inside the dining hall of Santa Maria delle Grazie in Milan, hammering a single iron nail into the dry plaster wall. He tied a string to the nail right at Christ's right temple, snapping lines across the surface to mark out the room's single-point perspective. It was a precise, slow-moving start. But the decisions Leonardo made over the next three years set off half a millennium of near-catastrophic bad luck.
Most visitors know that The Last Supper is fragile. Few realize it is a miracle the painting exists at all. Between a terrible DIY paint recipe, monks swinging hammers, stone-throwing soldiers, and an Allied bomb that blew down the surrounding building, Leonardo's famous mural has survived against almost impossible odds.
The Fatal Painting Recipe
Traditional Renaissance frescoes were painted on wet plaster. The pigment soaked deep into the wall as it dried, binding chemically with the lime. The catch? You had to work fast, finishing each patch before the plaster set. Leonardo hated being rushed. He wanted to sit, ponder, adjust a shadow, and come back three days later to touch up a single eyelash.
So he invented his own method. He coated the dry stone wall with a thick sealing layer of pitch, gesso, and mastic, then painted over it using an experimental mix of egg tempera and oil. It let him paint with the delicate glazing of an oil painting on wood panel. It also failed immediately.
The refectory wall sat right next to the convent kitchen and had a damp basement beneath it. Moisture got trapped behind Leonardo's impermeable pitch layer, pushing the paint off the wall from the inside out. By 1556, just sixty years after completion, art historian Giorgio Vasari visited Milan and reported that the mural was already half ruined, reduced to a blur of flaking scales.
The Day Monks Cut Off Jesus's Feet
By the 17th century, the painting had darkened so badly under layers of kitchen grease and mold that the resident Dominican monks stopped treating it like sacred art. In 1652, the convent decided their servers needed a shorter walk between the kitchen and the dining tables.
Their solution? They hammered a doorway straight through the bottom center of the refectory wall. In doing so, they chipped away the lower edge of the table and permanently amputated Jesus's feet, which Leonardo had painted resting beneath the cloth. If you look at high-resolution images today, you can still see the arch of that filled-in doorway standing right where Christ's legs used to be.
Fortunately, Leonardo's studio pupils had made full-scale copies on canvas art prints while the original was still intact. A 1520 copy by his student Giampietrino, now held by the Royal Academy in London, preserves those missing feet along with small details like the overturned salt cellar near Judas's arm.
Napoleon's Soldiers and Rock-Throwing Cavalry
In 1796, French revolutionary troops under Napoleon Bonaparte occupied Milan and requisitioned the convent. Napoleon himself issued a strict written order protecting the refectory wall, a sprawling display of horizontal wall art. His soldiers promptly ignored it.
The army turned the dining hall into a stable for cavalry horses and a storage barn for hay. Drunken soldiers slept on the floor, threw mud and rocks at the apostles' faces, and climbed ladders to gouge out the eyes of the figures painted with Renaissance realism art techniques. Moisture from horse breath and rotting straw accelerated the paint decay even further.
The WW2 Bomb That Left One Wall Standing
The biggest test of survival came on the night of August 15, 1943. Allied bombers struck Milan in a heavy air raid. A high-explosive bomb landed directly inside the refectory of Santa Maria delle Grazie.
The roof caved in. The side walls collapsed into mountains of rubble. But miraculously, the end wall holding The Last Supper stayed upright. Convent workers and Italian conservators had preemptively stacked sandbags and timber scaffolding against both sides of the wall. Although the painting survived the blast, it remained exposed to open air, rain, and humidity for months under temporary tarpaulins until a new structure could be rebuilt around it.
21 Years of Cleaning Up 500 Years of Disasters
By the 1970s, the mural was a mess of flaking paint, dirt, and clumsy overpaintings added by well-meaning restorers in the 18th and 19th centuries. In 1978, lead conservator Pinin Brambilla Barcilon began a monumental 21-year restoration project.
Working under microscopic lenses with surgical tools, her team spent two decades removing glue, wax, and heavy repainting dot by dot. When they finished in 1999, critics realized that only about 20 percent of Leonardo's original paint layer remained intact. Yet what was left was authentic Leonardo: brilliant tones of lapis lazuli, delicate gestures, and the exact psychological tension of the moment Christ reveals his coming betrayal.
Today, visiting The Last Supper requires booking weeks in advance. Guests pass through airlock filtration chambers to control humidity and dust before standing in front of the wall for a strict 15-minute limit. It is an elaborate defense system, but after 500 years of surviving bad chemistry, hammers, horses, and bombs, the painting has earned every bit of protection it can get.
Frequently Asked Questions
Why did Leonardo use an experimental technique instead of traditional fresco?
Traditional fresco required painting rapidly onto wet plaster before it dried. Leonardo preferred to work slowly, making deliberate revisions over months or years. His custom mixture of tempera and oil on dry plaster allowed for fine detail, but lacked the moisture resistance needed for a damp dining hall wall.
Can you still see the doorway cut by the monks?
Yes. The doorway was filled in during later structural repairs, but its rectangular arched outline remains clearly visible below the central tablecloth, directly beneath the figure of Christ.
How much of Leonardo's original paint is left on the wall?
Following the 1978–1999 scientific restoration led by Pinin Brambilla Barcilon, experts estimate that roughly 20 percent of the visible pigment represents Leonardo's original paint, with the rest preserved as faint fragments or stabilized underdrawing.
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