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Onset of Deterioration

When: 1498
Where: Convent of Santa Maria delle Grazie, Milan
Part of: Completion of Leonardo da Vinci's The Last Supper

The painting began to deteriorate soon after its completion in 1498 due to the tempera medium.

Because Leonardo used tempera on the wall rather than the proven fresco method, the painting began to deteriorate soon after it was completed. This technical choice is cited as the reason for the early degradation of the mural.

Sources

The Last Supper (Leonardo) Wikipedia, revision of 2026-07-26

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.