Unfortunately, The Last Supper did not stand the test of time and it began flaking and fading around 1518, only 20 years after its completion. This is because of da Vinci’s failed experimentation with painting materials instead of using traditional fresco techniques. Typically, tempera paint is applied directly onto the wet plaster of the wall which helps it affix to the painting, but its fast drying time meant an area had to be completed in one day’s work and could not easily be reworked later. This didn’t sit well with Leonardo, who preferred a leisurely style of applying thin paint layers over many hours, a style supported by his use of oil paint. He also didn’t have any previous fresco experience, so he decided to use a different approach for The Last Supper. He coated the wall with a layer of ground white stone and white lead primer before painting directly onto the dry plaster wall. He experimented with different proportions of oil and tempera paint in different parts of the painting, as he thought that mixing the types would allow him to still use his method of gradually applying thin layers of paint. However, his experimentation failed and the painting quickly faded and crumbled. When a biography of da Vinci was published in 1550, the author, Vasari, proclaimed that the painting was “ruined”. Today, very little of the original is left.

Sources:

Issacson, W. (2017). The Last Supper. In Issacson, W, Leonardo da Vinci. (pp. 273-292). New York, NY: Simon & Schuster

Harris, B. & Zucker, S. (n.d.) The Last Supper. Retrieved from https://www.khanacademy.org/humanities/ap-art-history/early-europe-and-colonial-americas/renaissance-art-europe-ap/a/leonardo-last-supper