The following excerpt from the Getty Institute' Introduction to Fresco Painting course handout developed by the Fresco School might be helpful:

Lime painting – a method in which fresco pigments are mixed with lime water or slaked lime; casein (or skim milk) can be added to increase adhesion. The wall is wetted down with lime water until the plaster softens or a paste of lime is laid upon the wall. This technique is also used in painting on setting plaster as a stage in the mezzo fresco technique. Pompeiian frescoes were often painted using mezzo fresco. Although it is a less demanding technique, the resulting painting has a more pastel or chalky quality, and is not as durable as Buon Fresco.

Buon Fresco or True Fresco – a painting method in which the artist must start applying his or her colors on the wet intonaco (painting plaster layer) as soon as it has been prepared and laid on the wall or ceiling. The plaster does not technically "dry" but rather a chemical reaction occurs in which calcium carbonate is formed as a result of carbon dioxide from the air combining with the calcium hydrate in the wet plaster.

Secco Fresco – a technique of applying colors onto dry plaster. Pigment is mixed with adhesives (i.e. binding mediums) such as egg, gum arabic, casein, animal skin glue, oils, or modern day acrylic. Results are not as durable as Buon Fresco and the painting will eventually flake off beyond repair. The Last Supper (c. A.D. 15th century) by Leonardo da Vinci is an unfortunate example of the limitations of the Secco technique.

Trullisatio or Scratch Coat – the first, base coat of plaster usually scratched with a trowel, hence the name. This coat is laid directly on the "chicken wire" mesh, lath stone, or brick.

Arriccio or Brown Coat – a layer of plaster over the scratch coat (trullisatio) and just under the finish coat of plaster (intonaco) which will be painted. The sinopia (full-scale composition) is created on the arriccio.

Intonaco - direct translation from Italian is "plaster", refers to a mixture of slaked lime and aggregate (other than marble powder, mainly sand) with a general proportion of 2-3 parts of aggregate to 1 part of lime. The word Intonaco is also used as a name for the final smoothest coat of plaster (5 parts lime to 8 parts aggregate) on which the actual Buon Fresco is painted before it dries and hardens.

Marmorino – a Roman plaster coat made of fine marble powder and lime putty (1 part lime to 1 part marble powder), this plaster coat is applied over intonaco. Greek origins, widely used in Ancient Rome for wall finishes and frescoes. However, this coat is very dense and usually polished which impairs absorption of paint. During the Renaissance, this coat was omitted and fresco painting was done directly on intonaco.

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