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Before creating a painting of any kind—whether you're using oils, acrylics or tempera paints—it's important to apply a primer to the surface upon which you're painting. One type of painting surface primer that's been around for centuries and is still used today is gesso. Its purpose is to prevent paint from soaking into the weave of the canvas or any other material.
How to Apply Gesso
Gesso can be sprayed on or applied with a brush onto a substrate such as canvas, panel, or paper, explains Ashley Nordin, education developer at BLICK Art Materials. "It can absorb layers of paint without any bleeding or seeping of the painting medium (i.e. oil stains). Gesso allows the surface to accept the paint, so that paint and mediums do not soak into the fibers of the substrate, which can ultimately cause long-term or severe damage to a painting."
What Gesso Is Made From
Gesso is a pretty simple material—it was originally made from a mixture of chalk or plaster and glue. In fact, the word "gesso" stems from the Italian word meaning "chalk." Today's gesso is typically a bright white mixture of calcium carbonate and acrylic polymer medium used on canvas, panels, or heavyweight paper, according to Nordin. "The chalk or plaster component of gesso makes it absorbent so that when paint is applied to a surface primed with gesso, the moisture wicks evenly from the paint without any bleeding or seeping of paint binders such as oils into the fibers of the substrate which can cause a breakdown of the painting in the long term," she says.
When to Use Gesso
While there are other types of primers out there, including latex, if you're painting with acrylic or oil, gesso is the best option. "This is because the calcium carbonate mixture and acrylic polymer medium are designed to be compatible with each other and help to better absorb those materials for an ideal color application," says Nordin. Needless to say, gesso is definitely an artist's studio essential. Nordin recommends always priming pre-stretched store-bought canvas with a couple layers of gesso prior to starting a painting, even if it has already been primed. "Practicing this step will help to retighten the surface if there are any minor dents in the canvas, as well as refresh and brighten up your background," she says. "Combine acrylic gesso with a small amount of water to help the primer glide along the surface, then apply two to three coats with a large brush, brushing each layer in in the opposite direction of the previous stroke before allowing layers to dry between applications." Once dry, she recommends lightly sanding using a fine grit sandpaper until the surface is smooth.
Different Types of Gesso
You can often find acrylic gesso in three grades: Studio, Artist, and Professional. The difference among these three grades, according to Nordin, is the amount of concentrated gesso in the formula. "The professional-grade gesso is highly concentrated and should be thinned with water for the best application," she says. "Artist-grade gesso is slightly less concentrated than its professional counterpart, and even less so with the Student-grade gesso that is almost ready for use right out of the container."
Because gesso has a "stiff" formula, it should be thinned down with water or paint thinner for an ideal, smooth application, according to Nordin. "Because of this, gesso acts as a modeling paste when it is applied in heavy amounts to a work surface and allowed to dry," she says. Its stiff formula can serve as a great way to create textures for abstract painting, notes Nordin, or to build an under layer of texture for a landscape painting. If you go this route and decide to create a sculptural texture with gesso, she recommends using a palette knife for the best results.