"Gesso" is the Italian word for "chalk" (akin to the Greek word "gypsum"), and is a powdered form of the mineral calcium carbonate used in art. Gesso was traditionally mixed with animal glue, usually rabbit-skin glue, to use as an absorbent primer coat for panel painting with tempera paints. This mixture is rather brittle and susceptible to cracking, thus making it unsuitable for priming canvas. The Needles, part of the extensive Southern England Chalk Formation For other uses, see Chalk (disambiguation). ... Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. // Chemical structure Heating gypsum to between 100°C and 150°C (302°F) partially dehydrates the mineral by driving off exactly 75% of the water contained in its chemical structure. ... Minerals are natural compounds formed through geological processes. ... Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... Rabbit-skin glue is a sizing that also acts as an adhesive. ... The Ghent Altarpiece: The Adoration of the Mystic Lamb, interior view, 1432. ... A 1367 tempera on wood by Niccolò Semitecolo. ... Canvas is an extremely heavy-duty fabric used for making sails, tents, marquees, and other functions where sturdiness is required. ...

Acrylic gesso

Modern acrylic "gesso" is actually a combination of calcium carbonate with an acrylic polymer medium and a pigment. It is sold premixed for both sizing and priming a canvas for painting. While it does contain calcium carbonate to increase the absorbency of the primer coat, Titanium dioxide or titanium white is often added as the whitening agent. This allows the "gesso" to remain flexible enough to use on canvas. High concentrations of calcium carbonate will cause the resulting film to dry to a brittle surface susceptible to cracking. Structure of methyl methacrylate Polymethyl methacrylate (PMMA) or poly(methyl 2-methylpropanoate) is the synthetic polymer of methyl methacrylate. ... Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... In biology, pigment is any material resulting in color in plant or animal cells which is the result of selective absorption. ... Canvas is an extremely heavy-duty fabric used for making sails, tents, marquees, and other functions where sturdiness is required. ... The examples and perspective in this article or section may not represent a worldwide view. ... Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ...

Acrylic gesso can also be colored, either commercially by replacing the titanium white with another pigment, such as carbon black, or by the artist directly, with the addition of an acrylic paint. Acrylic gesso can be odorous, due to the presence of ammonia and/or formaldehyde which are added in small amounts as preservatives against spoilage. Pre-gessoed canvases can be obtained commercially. Soot, also called lampblack or carbon black, is a dark powdery deposit of unburned fuel residues, usually composed mainly of amorphous carbon, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke—especially from the combustion of carbon-rich organic fuels in the lack of sufficient oxygen. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... The chemical compound formaldehyde (also known as methanal), is a gas with a strong pungent smell. ...

Acrylic gesso is a modern art material, and has an unproven record as a primer for oil paintings. Many of the solvents used in oil painting, such as turpentine or odorless mineral spirits (OMS), will leach some oil through a thin acrylic primer coat and damage the canvas underneath. And, while a pure acrylic polymer is more flexible than traditional animal size, the addition of calcium carbonate increases the brittleness of the primer coat. Thus, the archival nature of acrylic gesso on canvas is uncertain. Mona Lisa, Oil on wood panel painting by Leonardo da Vinci La Donna Velata, painted in 1516, Oil on wood panel painting by Raphael Oil painting is done on surfaces with pigment ground into a medium of oil — especially in early modern Europe, linseed oil. ... Turpentine is a fluid obtained by the complex distillation of resin obtained from trees, mainly various species of pine (Pinus). ... White spirit also known as Stoddard solvent is a paraffin derived clear, transparent liquid which is a common organic solvent used in painting and decorating. ...

Gesso and sculpture

Gesso is also used by sculptors, to prepare the shape of the final sculpture (fused bronze) or directly as a material for sculpting. A collection of gesso sculptures is properly called a gypsotheque. An Italian Futurist sculpture by Umberto Boccioni at the Museum of Modern Art in New York City (MoMA). ...