Gesso

Gesso is a preparatory ground used in painting to create a smooth, receptive surface on supports such as canvas, wood panels, or other rigid surfaces. It seals the substrate, controls absorbency, and provides tooth for subsequent layers of paint.

Traditional gesso is a paste made from a white pigment (historically gypsum or calcium carbonate, and sometimes lead white), a binder such as animal glue, and water. It is applied in thin coats to a primed surface and allowed to dry before sanding. Modern gesso products typically use an acrylic polymer binder with titanium dioxide as the white pigment, sometimes with calcium carbonate fillers. This acrylic version dries more quickly and is flexible enough for a range of media.

Preparation and application: For wooden panels, the surface is usually sized with a thin layer of glue to limit resin bleed, then coated with several thin gesso layers, with light sanding between coats to achieve uniform coverage. On canvas, gesso is applied to block the weave, creating a consistent ground; it may be tinted slightly or left white, and may also be sanded for a smoother or more toothy finish depending on the painter’s preference.

History and use: Gesso has been used since the Renaissance and earlier to prime panels and canvases for tempera and oil painting. Traditional gesso yields a hard, opaque ground, while acrylic gesso provides greater flexibility and easier maintenance. Both forms are widely used to prepare surfaces for various painting techniques.

Safety: Gesso dust should be minimized when sanding; use a mask to avoid inhalation. Modern products typically avoid toxic pigments, but historical formulations sometimes included hazardous materials, making contemporary formulations safer choices.