David Rockefeller, Jr.: To make his murals, Rivera used traditional Italian fresco-making techniques but applied them in innovative new ways. Conservator, Anny Aviram.
Conservator, Anny Aviram: Fresco comes from the Latin word fresh. Fresco is a process of building up layers of plaster onto the walls.
In the case of the Rivera panels for the exhibition in 1931 he had his assistants apply the plaster layers the trusillatio, which is the scratch coat. And then the arriccio coat, which is called a brown coat. This is applied to the trusillatio, and left a little bit rough so the top layer adheres easier.
David Rockefeller, Jr.: These first two layers of the fresco were prepared weeks ahead of time by Rivera's assistants. Meanwhile, Rivera created large-scale drawings of the murals.
Anny Aviram: To transfer the drawing to the arriccio layer you make little holes in the outline of the drawing with a little wheel and put it on the wet plaster. Along the perforated lines, with a cotton cloth bag containing black pigment, you will leave a fine dotted line as a guide for the artist to be able to draw on it. That’s called pouncing. You can clearly see it in the knot of the shirt of Zapata.
Then his assistants will apply the intonaco, which is the smoothest layer of all, the one that’s going to receive the paint.
So then, Rivera comes and starts underlining over the dotted lines. Then he starts painting, with a speed.
David Rockefeller, Jr.: Because plaster dries quickly, Rivera worked on the mural in sections. Each one is called a giornata, an Italian word that refers to a day's work.
Anny Aviram: In the case of The Agrarian Leader Zapata, we have identified three visible giornatas. One that runs across Zapata’s shoulder and around the top of the horse. The second one runs down the center of the fresco, including Zapata’s body. And the third one includes the life-size white horse.