Intonaco

Example of spray fireproofing, using a gypsum based plaster in a low-rise industrial building in Vancouver, British Columbia.

Intonacois an Italian term for the final, very thin layer ofplasteron which afrescois painted. The plaster is painted while still wet, in order to allow the pigment to penetrate into the intonaco itself. An earlier layer, calledarriccio,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.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 ofsand(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 onlime,where the only binding substance ishydrated lime
• Intonaco lime/cement, where the binding element is a mixture of hydrated lime withPortland cement,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

Thesandutilized in the intonaco can belimestoneorsilicate,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