Sinopia is the term for the preliminary underdrawing made in red ochre pigment (originally from Sinope on the Black Sea) on the rough intonaco layer of plaster before applying the final smooth plaster on which the fresco would be painted. This compositional drawing, executed in a reddish-brown earth colour, established the main lines of the composition before the painter began the time-sensitive work of buon fresco painting on wet plaster. When Renaissance frescoes were removed from walls in the 20th century for conservation — particularly after the Florence flood of 1966 — the sinopie beneath were revealed for the first time. They show the artist's spontaneous drawing style unmediated by the constraints of the final work — sometimes rougher, more immediate, more revealing of personality than the finished painted surface.