The city of Milan wanted the restoration completed for the 500th anniversary of the painting, but the years passed, and the scaffolding stayed in place as the restorers worked flake by flake, millimeter by millimeter, fragment after fragment.
But then again the painting was never really about speed anyway, was it.
When Leonardo was working on it, he had more than one unfriendly discussion with the Friars of the monastery of Santa Maria delle Grazie over his apparent lack of urgency to complete the project. They were becoming exasperated with his slowness. They complained that Leonardo would stand in front of the painting for hours, make a few brush strokes, and then leave for the day. It was true. Leonardo was taking his time. In fact it is precisely because he wanted to take his time that all the trouble began. Leonardo knew that if he used normal fresco techniques he would have to work quickly, and that was not his game plan. So he experimented and reworked an old Roman and Greek technique that would give him more time and allow him to work at his own pace.
Santa Maria delle Grazie, Milan
With true fresco, a layer of wet plaster is applied to a surface and before it dries the artist must apply the color. The color then penetrates the plaster and becomes part of it, and together they become an indestructible substance. The wet plaster layer is called la giornata, meaning the day, because that's all the time you have to work with it. Instead, what Leonardo did was put two layers of a dry plaster preparation on the wall, and he used the wall the same way a painter uses a canvas.
If he made a mistake, although it's hard to think of Leonardo making mistakes, all he had to do was slap on another layer of plaster and start over again. This technique gave him enough time; days, months and even years, to retouch, correct and modify portions of the painting he wasn't satisfied with. The problem was that the technique he used requires a number of special conditions, the most important of which is a dry wall, and the wall on which Leonardo painted the Last Supper was anything but dry, even today. In the winter moisture laden winds blow down on Milan from the snow-covered Alps, and in the summer water condenses on the wall because there is a river directly beneath the monastery. Not the best of conditions for a painting, to say the least.
Then came a series of restorations, one more damaging than the other. The painting was scraped, peeled, waxed, oiled, glued and destroyed. At one point restorers were reattaching Leonard's paint droppings with a mixture of glue and oil. At the end of the eighteenth century, art restorer Luigi Mazza decided to take all the glue and oil off. While he was definitely on the right track, in the process he also took off a great deal of what remained of Leonardo's paint.
And as if that wasn't damage enough, the building was completely destroyed by a bombduring the Second World War Newspapers of the day ran scandalous photos of the wall exposed to the elements, held up only by sacks of sand. The fact that the wall was standing at all would have been called a miracle in the Middle Ages, and maybe it was.
Today the painting is protected. Special dust-absorbing carpets and dust-filtering pipes have been installed to keep it safe from the elemnts. Reservations are necessary and visitors are only allowed inside in groups of 25 and only for 15 minutes. But it is 15 minutes in the presence of genius. If you are in town, and you can get a reservation, I highly recommend it. You’ll never look at a reproduction of the Last Supper in the same way again.