Much of the enthusiasm and esprit de corps among the artist at Coit Tower seemed to be generated by the medium of fresco. As Dr. Heil put it, “The technique of fresco is, in itself, a unifying influence… The artists established for themselves one scale and also one palette consisting of elementary earth colors.
The fresco painters at the Tower followed the old Italian traditions as the Mexican artist interpreted it. In this process, fine marble dust is mixed with slaked (pronounced “slaked”) lime to create the painting surface. Plasterers slake the line by firing it quickly in kilns, then soaking it in water---historically, in pits in the found, but nowadays in large vats---for about three months.
In fresco buono, the plasterer prepares the wall by building up a bed of cement and rough lime plaster on which the artist traces an outline or cartoon of the design. Early on the morning of the day that the artist is to paint, the plasterer spreads a thin smooth surface coat of fine wet plaster about two feet square, approximately in the shape of the outlined figures. Using a very small wet brush, the artist applies the earth colors, either dry or mixed with distilled water, repeatedly building up their intensity as long as the surface remains moist---up to twelve hours. Although it appears a solid color to the eye, under a microscope the fresco surface shows eight particles of white plaster “cupping” one color particle. To assure their uniformity, only one artist-assistant at Coit Tower, Farwell Taylor, ground all the color pigments for all the frescoes.
In fresco secco, the medium Jane Berlandina used in the egg tempera room on the second floor, the final plaster surface is allowed to dry. The artist may then use any of several media besides water: casein, oil paint, gums and resins, as well as egg tempera. Some artists begin a buono and then intensify by superimposing a secco colors. Thus, as the colors dries in or on the plaster, the picture becomes part of the wall; and changes moist be chipped out, for there is no altering or rubbing out once the design is begun. Although painted quickly in small sections, fresco lends itself to bold, direct designs, usually of free, simplified, and often vigorous forms and vivid colors, albeit limited by the earth color palette. Zakheim, for one, finding it a very exciting medium in which to work, likened the application of the brush on wet plaster to the bestowal of a kiss---not surprising when one remembers that the very word fresco is from the Italian a fresco: “fresh.”