What is a Fresco?

Fresco, the Italian word for fresh, is a form of mural painting in which earth pigments are painted directly on fresh, wet, lime plaster. As the plaster dries, a chemical process bonds the pigment and plaster together.

Because humid weather is ideal for fresco painting, work on the ceiling and pillars of the St. Thomas project was done only during the summer, when conditions were optimal. The project began in 1993, continued in 1994 and was completed in 1995.

Artist Mark Balma used the same materials and methods as the great Italian fresco masters, from Giotto to Tiepolo, on the Frescoes of St. Thomas. The Vatican quarry that provided lime for Michelangelo's fresco masterpiece, the Sistine Chapel ceiling, provided lime for the St. Thomas project. The paint brushes were specially made in Italy from boar's hair, which resists the lime's highly alkaline quality. Earth pigments, mined from sources around the world, were ground by hand, a crucial task that must be performed properly to ensure the stability of the pigments in the plaster. Even the time-honored method of mixing the plaster with a hoe in a trough proved to be superior to using a jackhammer-like mixing power tool.

To "build" a fresco, plaster is applied in several layers, starting with the rough arriccio layer and finishing with the intonaco coat. Because plaster dries quickly, only the area the artist can paint in one day is plastered. This is called a "day section." Unlike acrylic or oil, fresco painting cannot be covered over, thus making every stroke permanent. If the artist feels dissatisfied with some part, the plaster and paint either must be scraped off while still wet, or if dry, chipped off and the process started over again with the arriccio layer.

Maren Nelson, former administrative assistant at the Minneapolis Institute of Arts and an assistant to Balma on the St. Thomas project, explains the process of fresco painting: "Before the smooth intonaco coat is applied, the ceiling is gridded using a snap-line coated in sinopia, a red earth pigment. [These] mark the transfer of the design to the ceiling. The design, called a 'cartoon,'... is outlined on gridded tracing paper. The cartoon then is perforated with a small needle to create an image of the design. Next comes a step called 'pouncing,' [in which] tracing paper is positioned on the ceiling and tapped lightly with a muslin bag filled with dry charcoal. The pattern left on the plaster surface formed a kind of connect-the-dots road map for Balma and his assistants to follow. The perforated tracing paper was used twice, first to transfer the entire cartoon on to the rough plaster layer and then to mark each day's fresh intonaco coat.

"Fresco has a long and varied history. Following a visual tradition that began with the cave paintings at Lascaux more than 15,000 years ago, it has been used throughout the ages as a means of religious and secular communication. Fresco painting is not uniquely a Western convention, however; it is found around around the world on every continent.

"The American public is most familiar with frescoes painted by the great Italian masters. Cennino Cennini documented the techniques these artists used in The Craftsman's Handbook, written in 1437. Throughout the project, Balma referred to this and other sources daily.

"Fresco painting flourished in Italy in the late Middle Ages, an era of widespread building by the Catholic church and the government. The church used paintings on the walls and ceilings to teach religious doctrine to a largely illiterate public. In monumental frescoes they filled both didactic and aesthetic needs. They taught Christian history and dogma, promoted good citizenship, and harmonized with the architectural space for a completely unified interior. The artists took their mission very seriously. The Sienese painters' guild, for example, proclaimed themselves 'by the grace of God, the expositors of sacred writ to the ignorant who know not how to read.'

"While Balma and his apprentices had less lofty self-images, they were genuinely devoted to the fresco medium and its possibilities for conveying collective ideas to a diverse society. They were gratified that Balma, one of a handful of fresco artists in the world, initiated a fresco renaissance reminiscent of the efforts of Mexican muralists Diego Rivera, Jose Clemente Orozco and David Alfaro Siqueiros in the 1930s.

"Today, fresco appears to be enjoying renewed interest and acclaim, perhaps because of the decade-long restoration of the Sistine Chapel begun in the 1980s. In addition, the technique's emphasis on natural materials and skilled artistry may appeal to a world weary of mass production and shoddy quality. That there is nothing careless in the preparation and execution of a fresco is evident in the last step of the process. Because some pigments, particularly blues such as lapiz lazuli, cannot withstand the caustic nature of the lime, they are applied with an egg tempera after the fresco has dried. Balma's assistants became quite adept at separating the yolk from the egg white, meticulously rolling the yolk in their hands to remove every remnant of white. They gingerly held the yolk sac above a jar, then pricked it with a pin and mixed its contents with the pigments."