Most artists are familiar with the word gesso. It is an important art supply that is used in sculpture, painting, gilding, and mixed media.
Gesso was traditionally made from chalk (in fact, gesso is Italian for chalk), plaster and gypsum. The chalk gave gesso its distinct white color, though in some cases, another mineral like zinc is substituted. Today, thanks to the innovations of a company called Liquitex, most gesso is water-based and is made of acrylic polymer medium and a white pigment made from titanium dioxide or titanium white.
Gesso looks like paint, but is actually thinner and more translucent—at least, when mixed with water—but becomes thick when dry. It was first used as a primer or a way of preparing the surface for a painting. The rougher surface yielded by the gesso layer made the surface rougher or “toothier.” This not only yielded delightful texture (some artists intentionally add multiple layers of gesso for a slightly raised or three-dimensional effect) but served the practical purpose of preventing the paint from seeping into the canvas or wood, or warping the paper.
Gesso was originally sold in pure white. However, there is now black gesso. Artists can also combine gesso with acrylic paint or even watercolor to create a faintly tinted primer. For greater convenience artists can also buy pre-gessoed canvases.
Gesso also has its uses in sculpture, where it is molded and shaped, or used to create “body” in relief designs and even manuscript illumination. Mixed media artists also use Gesso to create raised surfaces on canvas or wood, where they can press found objects or make a three-dimensional figure.