October 2008 Archives

Los Angeles based Fresco School (FrescoSchool.org) is proud to announce it's new Video Channel at www.YouTube.com/FrescoSchool

The new channel features video clips and video tutorials on fresco painting technique. Fresco Video Channel opens with the release of the detailed video tutorial on fresco plastering tools.

"Fresco Painting is the Mother of all Arts and as the channel progresses a variety of "YouTube size" art education videos will be added, including cartoon (drawing for fresco) painting, composition, color and other disciplines of fine art, decorative art and painting with focus on applied arts." - said iLia Anossov (fresco), founder of the Fresco School

Lime Putty is the main ingredient of the buon fresco painting.

Preparation of painting surfaces for fresco involves the application of plaster of increasingly finer texture.

The first step (which in nowadays mainly done by the factories) is the heating (calcination) of marble or limestone (calcium carbonate, CaCO3) at 800-900ßC to make porous lime (calcium oxide, CaO).

HEAT + CaCO3(s) ----> CaO(s) + CO2(g)

To form the plaster for fresco work, the lime is "slaked." The slaking process, which requires the addition of 2 or 3 molecules of water for each molecule of lime, yields calcium paste or lime putty, an aqueous gel of thin crystals of calcium hydroxide.

CaO(s) + H2O(l) ----> Ca(OH)2(s) + HEAT

Excess water acts as a lubricant so that the crystals slide easily over one another. Historically, lime was slaked in pits or troughs over a period of at least six months to obtain lime putty of the desired consistency. Artisans in Michelangelo's time use plaster aged for as long as ten years. Fresco plaster itself is made from the slaked lime and varying portions of sand or marble dust. Generally, walls are plastered with several layers of such fresco plaster in order of decreasing proportions and particle size of sand. Hardening of the fresco plaster on the wall includes several simultaneous physical and chemical process: the absorption of water into the wall, evaporation of water from the surface, and the carbonation of the slaked lime by carbon dioxide, CO

Ca(OH)2(s) + CO2(g) ----> CaCO3(s) + H2O(l)