Fresco (plural frescos or frescoes) is a technique of mural painting executed upon freshly laid, or wet lime plaster. Water is used as the vehicle for the dry-powder pigment to merge with the plaster, and with the setting of the plaster, the painting becomes an integral part of the wall. The word fresco (Italian: affresco) is derived from the Italian adjective frescomeaning "fresh", and may thus be contrasted with fresco-secco or secco mural painting techniques, which are applied to dried plaster, to supplement painting in fresco. The fresco technique has been employed since antiquity and is closely associated with Italian Renaissance painting.
Technology
Buon fresco pigment is mixed with room temperature water and is used on a thin layer of wet, fresh plaster, called the intonaco (after the Italian word for plaster ). Because of the chemical makeup of the plaster, a binder is not required, as the pigment mixed solely with the water will sink into the intonaco, which itself becomes the medium holding the pigment. The pigment is absorbed by the wet plaster ; after a number of hours, the plaster dries in reaction to air : it is this chemical reaction which fixes the pigment particles in the plaster.
The chemical processes are as follows:
calcination of limestone in a lime kiln: CaCO3 → CaO + CO2
slaking of quicklime: CaO + H2O → Ca(OH)2
setting of the lime plaster : Ca(OH)2 + CO2 → CaCO3 + H2O
In painting buon fresco, a rough underlayer called the arriccio is added to the whole area to be painted and allowed to dry for some days. Many artists sketched their compositions on this underlayer, which would never be seen, in a red pigment called sinopia, a name also used to refer to these under- paintings. Later, new techniques for transferring paper drawings to the wall were developed.
Copyright 2024 puzzlefactory.com All rights reserved.
