Gesso is a white or tinted primer compound traditionally made from chalk, gypsum, or calcium carbonate combined with a binder. It is used to prepare and seal surfaces such as canvas, wood panels, and picture frame mouldings, creating a stable ground for painting, gilding, or other decorative finishes. Modern formulations often include acrylic polymers, while traditional recipes relied on rabbit-skin glue and natural pigments.

Properties

Sealing agent: Prevents paint, gilding, or adhesives from sinking into porous substrates.
pH-neutralizing: Calcium carbonate helps neutralize acidity, stabilizing the surface for longevity.
Tooth/texture: Provides a slightly absorbent and textured surface, allowing paints and gilding layers to adhere properly.
Versatility: Can be sanded smooth for detailed work or left textured for expressive surfaces.

Common Uses

Canvas preparation: Priming raw canvas before oil, acrylic, or tempera painting.
Panel painting: Used historically in icon painting and Renaissance works to seal wooden panels.
Frame finishing: Applied to wood mouldings before gilding or decorative finishing.
Conservation: Serves as a ground layer in restoration projects when rebuilding lost paint surfaces.

Best Practices

Choose true gesso (made with rabbit-skin glue and chalk) for traditional oil painting or gilding.
Use acrylic gesso for modern applications with acrylic paints; it remains flexible and less prone to cracking.
Apply multiple thin coats, sanding between layers if a smooth surface is desired.
Allow each layer to cure fully before painting or gilding to prevent adhesion issues.
Store unused gesso in airtight containers to avoid premature drying or spoilage (for natural formulations).

Limitations

True gesso: Brittle when dry; not recommended on flexible supports like canvas unless carefully applied.
Acrylic gesso: Less absorbent than traditional gesso, which can affect the way oil paints sit on the surface.
Incompatibility: Oil paint should not be applied directly to unprimed canvas; without gesso, deterioration occurs more quickly.

Historical Importance

Gesso has been used since antiquity, with notable applications in Egyptian funerary portraits, Byzantine icons, and Renaissance panel paintings. Its role in gilding frames and artwork preparation remains central to both historical craftsmanship and modern conservation practices.

Gesso