this work, Leonardo sought a greater detail and luminosity than could be achieved with traditional fresco.[11] He painted The Last Supper on a dry wall rather than on wet plaster, so it is not a true fresco. Because a fresco cannot be modified as the artist works, Leonardo instead chose to seal the stone wall with a double layer of dried plaster.[11] Then, borrowing from panel painting, he added an undercoat of white lead to enhance the brightness of the oil and tempera that was applied on top. This was a method that had been described previously, by Cennino Cennini in the 14th century.
However, Cennini had recommended the use of secco for the final touches alone.[12] These techniques were important for Leonardo's desire to work slowly on the painting, giving him sufficient time to develop the gradual shading or chiaroscuro that was essential in his style