Intonaco is an Italian term for the final, very thin layer of

plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...

on which a

fresco Fresco ( or frescoes) is a technique of mural painting executed upon freshly laid ("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 become ...

is painted. The plaster is painted while still wet, in order to allow the pigment to penetrate into the intonaco itself. An earlier layer, called arriccio, is laid slightly coarsely to provide a key for the intonaco, and must be allowed to dry, usually for some days, before the final very thin layer is applied and painted on.Ugo Procacci, in ''Frescoes from Florence'', pp. 15-25 1969, Arts Council, London, gives a full account of the process. In Italian the term intonaco is also used much more generally for normal plaster or mortar wall-coatings in buildings. Intonaco is traditionally a mixture of

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

(with granular dimensions less than two millimeters) and a binding substance.

Types of intonaco

Different types of intonaco are classified based on the binding material used: * Intonaco based on lime, where the only binding substance is

hydrated lime Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula calcium, Ca(Hydroxide, OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed with water. A ...

* Intonaco lime/cement, where the binding element is a mixture of hydrated lime with

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar (masonry), mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in th ...

, with a majority of lime * Intonaco cement/lime, where the binding element is a mixture of hydrated lime, and Portland cement, with a majority of Portland cement * Intonaco with a plaster base, where the binding element is exclusively plaster The

utilized in the intonaco can be

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

silicate A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used ...

, taken from a natural source such as a river or from sand that is pulverized.

Types of stabilizers

Intonaco can be stabilized using: * Lime * plaster * Calcium-sulfate based plaster * Terracotta-based cement

References

{{reflist Painting techniques Plastering