A restored gesso panel representing St. Martin of Tours, from St. Michael and All Angels Church, Lyndhurst, Hampshire Gesso (; '

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

', from the , from ), also known as "glue gesso" or "Italian gesso", is a white

paint Paint is a material or mixture that, when applied to a solid material and allowed to dry, adds a film-like layer. As art, this is used to create an image or images known as a painting. Paint can be made in many colors and types. Most paints are ...

mixture used to coat rigid surfaces such as wooden painting panels or masonite as a permanent absorbent primer substrate for

painting Painting is a Visual arts, visual art, which is characterized by the practice of applying paint, pigment, color or other medium to a solid surface (called "matrix" or "Support (art), support"). The medium is commonly applied to the base with ...

. It consists of a binder mixed with

, gypsum,

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

, or any combination of these. Gesso is used in painting as a preparation for any number of substrates such as wood panels,

canvas Canvas is an extremely durable Plain weave, plain-woven Cloth, fabric used for making sails, tents, Tent#Marquees and larger tents, marquees, backpacks, Shelter (building), shelters, as a Support (art), support for oil painting and for other ite ...

and sculpture as a base for paint and other materials that are applied over it.

Characteristics

The colour of gesso is usually white or off-white. Its absorbency makes it work with all painting media, including water-based media, different types of tempera and

oil paint Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. Oil paint also has practical advantages over other paints, mainly because it is waterproof. The earliest surviving ...

. Mixing and applying it is a craft in itself, as it is usually applied in ten or more extremely thin layers. The hide glue mixture used to make the traditional gesso is rather brittle and susceptible to cracking, thus making it suitable for rigid surfaces only. When painting, there are several advantages to using gesso. It provides a strong foundation for the paint to adhere to, prevents the paint from soaking into the surface, and can also be used to achieve a desired texture or surface finish. Furthermore, gesso can help to extend the life of a painting by acting as a barrier to protect it from moisture, dust, and ultraviolet (UV) light.

Composition

Acrylic gesso Gesso is traditionally a mix of an animal glue binder (usually rabbit-skin glue), chalk, and white pigment. For priming flexible

, an

emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...

of gesso and

linseed oil Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colorless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...

, also called "half-chalk ground", is used. Acrylic gesso is a mixture of white pigment and some kind of filler (chalk, silica, etc.) and acrylic resin dispersed in water. It produces a soft, flexible non-absorbent surface that is technically not ''gesso'' (although it is commonly called that by its manufacturers). It can contain calcium carbonate (CaCO₃) to increase the absorbency of the primer coat as well as

titanium dioxide Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound derived from titanium with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or Colour Index Internationa ...

or "titanium white" as a whitening agent. It is sold premixed for both sizing and priming panels and flexible

for

. Art supply manufacturers market canvases pre-primed with acrylic gesso. Acrylic gesso can 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 Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

or formaldehyde, which are added in small amounts as preservatives. Acrylic gesso's non-absorbent acrylic polymer base makes it incompatible with media that require an absorbent substrate, such as egg tempera. ''The Painter's Handbook'' notes a problem with using oil paints over an acrylic gesso ground instead of a traditional oil ground, citing a mismatch in flexibility that over time could cause the oil paint to delaminate.

Uses

Sculptors may use gesso to prepare the shape of a final sculpture (fused bronze) or directly as a material for sculpting. Gesso can also be used as a layer between sculpted wood and gold leaf. In this case, a layer of refined and coloured clay called bole is used to cover the gesso before applying the gold. Bole is usually red in colour. Gesso can also serve as a base on three-dimensional surfaces for the application of paint or gold leaf.

References

External links

*
"The Technique of Raised Gilding", Jerry Tresser, 1992
* {{cite journal, author=Crane, Walter, author-link=Walter Crane, title=Gesso Work, journal=The Studio, volume=1, issue=2, date=May 1893, pages=45–49, url=https://babel.hathitrust.org/cgi/pt?id=pst.000068818081;view=1up;seq=57 Gilding Painting materials Italian words and phrases