In our series Sticks & Stones, we take a deep dive into medium. Each installment features one of art history’s most significant materials—its history, evolution, and unusual uses. (See past installments.) This week’s medium is plaster (explore the playlist).

The oldest known artworks were painted and drawn across walls, deep underground on the smooth, clay-rich caves of Lascaux. The early painters who made them were no doubt attracted to the even surface, and how well their pigments adhered to it; 17,000 years later, the brightly colored images are still clear.

With so many variables present in the painting process, a smooth surface is the only constant—one reason plaster has been a favorite throughout art history. Made from a mixture of lime, powdered cement or sand, and water, plaster is a liquid that dries solid. The ability to manipulate the material while in liquid form makes it a multifaceted medium. It can be used for plaster-based gesso paint to prime canvases, plaster-dipped fabric strips applied to smooth wooden panels, and perhaps most notably, fresco: the practice of painting pigment directly onto wet plaster.

Many of the greatest masterpieces of European painting were executed as wall or ceiling frescoes. Large works, like Michelangelo‘s Sistine Chapel ceiling, were painted onto a thin layer of wet plaster called intonaco. While most paints work by suspending pigment in a binding medium (like oil), when painting a fresco, the pigments bind to the wet intonaco layer so that the plaster binds them. This has made fresco one of the most durable and longest lasting types of painting. Because the pigments forming the decorative images are sealed into the plaster (rather than painted on top), they are safe from flaking, warping, and peeling over time. Many ancient frescoes dating back to the classical period have been unearthed by archaeologists over the years, their colors still bright and crisp. The word fresco means ‘fresh,’ referring to the fresh layer of wet plaster which must be laid down to absorb the applied color. When painting a large surface, like an entire wall or ceiling, a small section called the giornata (meaning ‘day’s work’) is painted over the rough underlayer, known as the arriccio. The next day, once the section has dried, any unpainted plaster is scraped off and mistakes from the day before are touched up with a secco (‘dry’) layer of paint.

Michelangelo’s Sistine Chapel ceiling is one of the largest. most ambitious frescoes ever made. The undertaking was commissioned by Pope Julius II in 1508, though it took Michelangelo over four years to complete. In order to work, the artist scaffolded half the room at a time, working on the massive space in piece-by-piece giornata. Unlike many artists of the time, who created full-scale drawings or ‘cartoons’ of the composition to transfer onto the fresco wall, Michelangelo would paint or draw directly onto the plaster. The monumental work consists of 9 central panels entirely surrounded by smaller scenes, containing a staggering total of 343 figures. Despite the Sistine Chapel ceiling being one of art history’s most famous painted works, Michelangelo identified himself as a sculptor, not a painter, and was miserable throughout the multi-year process of working on the ceiling. He began work at the end furthest from the altarpiece, working meticulously on each small giornata section. He was so eager to finish that by the time he reached the final panel of God in the act of creation, his style had loosened to the point that he could paint the entire famous scene in a single day. Michelangelo’s despondency about the enormous project is, of course, overshadowed by its lasting impact. The poses of his Sistine ceiling figures are some of the most frequently copied. The creation of the Adam scene in particular holds a place, alongside the Mona Lisa, as one of the most iconic images of Western art.

Fresco painting reached its peak of popularity during the Renaissance. The decline of the style was largely due to the emergence of a middle class, as newly wealthy patrons from outside of the church wanted to be able to commission smaller, more portable art for their private homes. Today, few people working with fresco paint directly into wet plaster. However, frescoes hold a central place in art history and the use of plaster as an art material remains prevalent as the smooth base of almost all canvas painting.