Gesso is a white paint

Paint

Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 mixture consisting of a binder

Binder (material)

-See also:*Adhesive or Glue*Cement*Paint...

 mixed with chalk

Chalk

Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

, gypsum

Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

, pigment

Pigment

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

, or any combination of these. It is used in artwork

Work of art

A work of art, artwork, art piece, or art object is an aesthetic item or artistic creation.The term "a work of art" can apply to:*an example of fine art, such as a painting or sculpture*a fine work of architecture or landscape design...

 as a preparation for any number of substrates such as wood panels, canvas

Canvas

Canvas is an extremely heavy-duty plain-woven fabric used for making sails, tents, marquees, backpacks, and other items for which sturdiness is required. It is also popularly used by artists as a painting surface, typically stretched across a wooden frame...

 and sculpture as a base for paint and other materials that are applied over it.
"Gesso", also known "glue gesso" or "Italian gesso" is a traditional mix of an animal glue binder, usually rabbit-skin glue

Rabbit-skin glue

Rabbit-skin glue is a sizing that also acts as an adhesive. It is essentially refined rabbit collagen, and was originally used as an ingredient in traditional gesso.-History:...

, chalk, and white pigment, used to coat rigid surfaces such as wooden painting panels

Panel painting

A panel painting is a painting made on a flat panel made of wood, either a single piece, or a number of pieces joined together. Until canvas became the more popular support medium in the 16th century, it was the normal form of support for a painting not on a wall or vellum, which was used for...

 as an absorbent primer coat substrate for painting

Painting

Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...

.