Fresco is a painting technique in which paint is applied to a wet plaster wall, or “intonaco,” so that the color of the paint absorbs into the wall as it dries. Rather than applying paint to an already-dried wall, this method permanently sets the painting on the wall, as evidenced by a matte, less shiny finish. Paintings done in this manner are typically larger in scale than traditional paintings, which is why large walls are preferred surfaces. The fresco paintings on the ceiling of the Vatican City’s Sistine Chapel, where Renaissance man Michelangelo painted many of the Bible’s most famous stories and characters, are probably the most famous.
The word “fresco” means “fresh” in Italian, most likely referring to the fresh and still-wet plaster wall that served as the canvas. Frescoes can be traced back to 30,000 years ago, when they were discovered in limestone caves in France and Spain, depicting animals such as horses, lions, bison, and even the extinct mammoth. The use of limestone plaster began in 1500 BC and spread throughout the Mediterranean, particularly in Egypt, Greece, and Morocco, where the frescoes were used for religious purposes, as many were found in tombs and burial sites. Plaster painting samples were also discovered in some Asian countries, including India and Turkey.
Aside from the freshly plastered wall, the paint itself is an important part of a fresco painting. The paint is traditionally made from naturally derived ground pigments that are mixed with water. After that, a brush is used to apply the paint to the wet plaster, and both components are dried at the same time. The painter, or “frescoist,” usually uses red chalk or the “sinopia” to draw the general outline of the painting.
Depending on the freshness or wetness of the plaster surface, there are three general types of frescoes. The first is the “buon fresco,” which means “true fresh” in Italian, because it uses the wettest plaster for the surface. The pigment is mixed with only water and applied to wet plaster, which absorbs the paint completely as it dries. To maintain its dampness, the plaster is applied to the wall in sections, depending on how much work the painter can complete in a single session.
The second type is called “mezzo-fresco” or “middle fresh,” because the plaster is only slightly damp but not wet enough to leave fingerprints. This method only allows for a moderate amount of paint absorption. The “a secco,” or “dry,” type of fresco painting uses dry plaster as the canvas, which necessitates the use of a pigment binding agent other than water, such as an egg yolk, oil, or glue. This allows the paint to adhere to the wall but not really penetrate it. The a secco method was used by Leonardo Da Vinci to create his famous painting “The Last Supper.”