The focus of the exhibition Diego Rivera: Murals for The Museum of Modern Art, currently on view on the second floor, is a set of “portable murals” Rivera made for his retrospective exhibition at MoMA in 1931. These works were the artist’s clever solution for displaying murals—paintings that typically are fixed on the walls of buildings—in the context of a temporary museum show. One of these portable murals, Agrarian Leader Zapata, is in MoMA’s collection, which allowed us to do extensive technical studies in preparation for the current exhibition. These tests provided a wealth of new details about how Rivera constructed his mural panels. When the time came to figure out a way to transport three of these works from Mexico City and install them in our galleries, we were glad to have this information on hand.
Rivera used traditional fresco technique, a centuries-old method for making extremely durable murals, to create his famous cycles in Mexico. MoMA conservators Anny Aviram and Cindy Albertson, who were invaluable partners in putting this exhibition together, took up the challenge of pinpointing how Rivera adapted this ancient technique to make his murals portable. They started by taking a closer look at Agrarian Leader Zapata’s internal structure.
Faint outlines of a diamond-shaped form are visible on the work’s reverse side (below left), so Anny and Cindy decided to X-radiograph the panel in hopes of getting a better view. They had to take 36 separate shots to cover the work since it measures approximately 8 x 6 feet! They next developed the X-ray film, scanned it to make digital files, and then overlaid the digital images to give a view of the panel in its entirety. Thanks to Anny and Cindy, we now know what the interior skeleton of one of Rivera’s portable murals looks like: stainless-steel bars, iron mesh, and a rigid outer frame work together to provide a sturdy, torque-resistant armature for the portable mural (below right).
Our conservators also conducted tests to determine the exact materials Rivera used. First, commercial concrete mixed with plant fibers to enhance stability was poured into Agrarian Leader Zapata’s metal framework. On top of this cement-and-metal foundation, Rivera then closely followed traditional fresco procedures, building up successively finer layers of fresco mortar (composed of lime, marble dust, and water) until they achieved an incredibly smooth surface. While the final layer was still wet, Rivera brushed on fine, hand-ground pigments (made from minerals and plants) suspended only in water. As the fresco dried, the lime in the mortar reacted with the air to create a hard layer of calcium carbonate. This chemical reaction effectively fused the pigments to the work’s surface. The key, then, to freeing the murals from an architectural setting was Rivera’s ingenious decision to combine an age-old recipe for making frescoes with materials commonly used in modern architecture, like cement and steel.
Rivera knew he couldn’t finish painting an entire mural in a day, given their size and the fact that he had to paint while the surface was still wet. So, just like generations of fresco painters before him, he broke the task down into sections that he could finish in a single session. One of these sections is called a giornata, the Italian word for day. Using reflectance transformation imaging, Anny and Cindy discovered that Agrarian Leader Zapata has three giornate. In other words, Rivera completed the work in three separate campaigns (left). As you can see from the diagram we created to map the giornate, Rivera was very careful to hide breaks in the surface mortar along the edges of figures in the composition. Standing in front of the work, the seams are barely noticeable to the naked eye. We have gathered so much great new information about Rivera’s working process that we dedicated a special section of the exhibition website to explaining giornate and many other aspects of fresco painting.
The hefty supports Rivera designed for his portable murals freed them from the wall, but they hardly made for easy transport. The largest panels weigh nearly 1,000 pounds! In order to bring them safely to New York, we teamed up with specialists in fresco conservation from Mexico, as well as structural engineers, architects, and crate makers. We even chartered a special cargo plane to fly directly from Mexico City to New York to avoid exposing the murals to extra bumps and vibrations. Once in the gallery, a group of expert art handlers used a forklift to slowly move each panel onto a specially designed platform (right). We knew from our extensive study of Agrarian Leader Zapata that we needed to support the murals from the bottom and avoid putting pressure on their delicate edges. In the end, the hard work paid off, and Rivera’s portable murals look wonderful reunited for the first time in 80 years.