In painting, the term fresco (pl. frescoes) comes
from the Italian phrase buon fresco, ("really fresh")
a technical term in opposition to in secco ("on dry surface").
True, or buon fresco, technique consists of painting in pigment
in a water medium on wet or fresh lime mortar or plaster. In secco
painting is done on dry plaster and with the pigments in a binding
medium, like egg. The difference between the two techniques is that
the wet plaster as it dries absorbs the pigment and the painting
becomes part of the wall surface rather than resting on top of it.
This makes a very durable work of art; if the wall is destroyed
the painting can often be reassembled because of the size of the
Because of the need to work on freshly laid plaster,
careful study of the wall surface can reveal the area worked on
in one day. In Renaissance Italy this was commonly called a giornata
or a "daily amount." These divisions are perceptible with
mild magnification (or even the naked eye if the plastering technique
was not good). Andrea Palladio, the famous Italian architect of
the 16th century, built many mansions with plain exteriors and stunning
interiors filled with frescoes.
Painters in fresco will often add details later
Egyptian wall paintings in tombs are usually in
secco, while the Roman wall paintings at Pompeii and Herculaneum
are in fresco.