Modeling The representation of a 3-d form on a 2-d surface, usually achieved through the variation of light and shadow across the depicted form. This modulation of light makes the form appear solid, round, and palpable. For forms modeled with extreme contrast between light and dark see chiaroscuro; for those shaped with subtle gradations of light, see sfumato.

Chiaroscuro The effects of light and shadow in a painting, particularly when the contrast between the two is very prounouced. The term is most often associated with the paintings of Caravaggio and Rembrandt. This dramatic illumination is often characterized by a shaft of light like that produced by a spotlight, which results in strong highlights and sharply cast shadows. Left: Rembrandt. Right: Caravaggio

Sfumato The imperceptible gradation of tones or colors from light to dark in modeling, often giving forms soft contours and creating perceptions of depth, volume and form. In Italian sfumato means "blended" with connotations of "smoky" and is derived from the Italian word fumo meaning 'smoke'. Leonardo described sfumato as 'without lines or borders, in the manner of smoke or beyond the focus plane.

Foreshortening The technique of depicting an object so it appears to recede. Forms lying at an angle to the picture plane are proportionately compressed to obtain the illusion of their extension into space. The term is applied to individual things or their parts as opposed to perspective, which refers to the overall construction of the space.

Pentiment [pentimento; It.: ‘repentance’]. Visible evidence of an alteration to a painting or drawing that suggests a change of mind on the part of the artist. In particular, it refers to previous workings (see also Underdrawing) revealed by the change in the refractive index of oil paint that occurs as it ages: thin layers of paint that were originally opaque may become semi-transparent. Pentimenti suggest that painters refined and altered compositions as they worked, and, for this reason, they are often cited as evidence of authenticity; similarly, they are less likely to appear in copies. The term is also used to describe the hesitant preliminary workings that show beneath some drawings.Underdrawing Note the pentimento regarding the hand position.

Iconography One of the principal concerns of iconography is the discovery of symbolic and allegorical meanings in a work of art

Supports and Ground

Ground. Preparatory coating or foundation layer on a Support that renders it more suitable for the application of paint or other artists’ media. The term ‘priming’ is often interchanged with the term ‘ground’, though technically it is possible to differentiate between them. A priming is the material applied to create a ground. In the 17th century the use of solid, dull-coloured grounds influenced technique and encouraged the use of paint in variable thicknesses, with dense, opaque paint being massed in the highlights. The paintings of Rembrandt are an extreme example of this, though in addition to dark grounds he favoured double grounds, consisting of a coloured ground over which a priming of another colour is applied Left: Picasso, Demoiselles. This detail shows how the white ground was used as a contrast to the painted areas, even those that are painted white, providing a subtle and luminous sense of space in these passages. Bruegel, showing detail of dark ground

Gesso In the strictest sense, gesso refers to a mixture of calcium sulphate (gypsum) and rabbit- skin glue that is applied in liquid form as a primer to the surface of a painting support. In broader usage, the term has come to refer to many types of similar white preparatory layers, including those made from chalk, as well as modern synthetic adhesives. The gesso layer smooths out irregularities in the support; it is usually applied in many thin layers and sanded and polished between applications.

Paintings in Cross-Section Left: Cross-section view of paint sample showing layers of ground, paint, and varnish

Wood panel Until the early 16th century the most important support for easel paintings was the wood panel. Wood, if carefully chosen, carpentered, and prepared, makes an excellent support on which to paint. This well preserved poplar panel still retains the original horizontal battens used to reinforce the panel support

Stretcher. Wooden framework that serves as a support for a painting on stretched canvas. Large stretchers usually have several cross-members to keep them rigid. Since the 18th century, stretchers have been designed with triangular keys or wedges at each corner. These allow the stretcher to be expanded to increase the tension on the canvas, which may become slack with age.

In this detail, the weave of the fabric support is clearly visible on the surface of this early canvas painting. Canvas. Type of strong, substantial cloth originally made of hemp (Cannabis sativa, from which it takes its name) but more likely to be of a coarse flax or tightly woven linen; similar textiles of cotton or jute are also called canvas. A cloth type rather than a specific cloth, with varied practical applications, canvas is important as a material used for making painting supports. ‘Canvas’ has therefore come to mean not only the raw cloth but also a piece of fabric mounted on a stretching frame and prepared for use in painting or a finished painting, usually in oils, painted on a textile support.

Painting techniques

Medium. Term used to refer to the actual physical material chosen as a vehicle of expression for any work of art. In painting it is used more specifically for the liquid in which the Pigment is suspended. By diluting the vehicle (the liquid binding agent in which the pigment particles are dispersed), the paint is made thinner and easier to apply.

Encaustic A wax based paint. Encaustic paintings were created by mixing pigment with molten wax (such as beeswax) and applying the mixture to a support while still hot. After the colors have been complete applied, the entire picture is heated slightly in order to fuse the painte layers together. Encaustic is most comonly associated with Egyptian portraits, and was rarely used again until the 20 th century. Jasper Johns (American, born 1930) White Flag, 1955 Encaustic, oil, newsprint, and charcoal on canvas H. 78-3/8, W /4 in. Metropolitan Museum

Fresco Wall painting technique in which pigments are dissolved in water only and then applied to fresh, wet lime plaster (the intonaco). As the wall dries, the calcium hydroxide of the plaster combines with carbon dioxide in the atmosphere to form calcium carbonate. During this process the pigments become an integral part of the wall, forming a fine, transparent, vitreous layer on its surface. Fresco is particularly vulnerable to damp and for this reason is suitable only for dry climates. Fresco Technique 1. Laying down the intonaco, 2. and 3. using cartoon with pin pricks and chalk powder to transfer drawing to wall. 4. painting.

In this egg-tempera portrait, the form has been created by many parallel strokes of color Tempera Type of painting medium used to bind pigments. Strictly, and as used by Cennino Cennini in his Libro dell’arte, the term may be applied to any combination of pigment and medium. By the 16th century, however, Vasari used the term specifically to mean egg tempera, a paint made using egg yolk as the binding medium, and this is the meaning now generally understood.

Egg tempera Egg tempera dries first by the evaporation of the water, followed by the setting of the egg proteins to a hard and eventually waterproof film. This determines the handling properties of the medium. Since the evaporation of the water leads to the loss of a considerable part of the volume of the paint film, the paint cannot be applied thickly or with brushmarked impasto as in oil paint (which sets with little loss of bulk). Too thick an application of tempera, contracting as it dries, may result in the cracking of the paint film and surface flaking. The paint film, therefore, has to be built up gradually by repeated thin applications. This method allows the water to evaporate rapidly and the egg medium to harden sufficiently to allow further layers, providing the brushstrokes are made with a light and rapid touch. If attempts are made to manipulate the paint and to blend the colours when wet, as in oil painting, the previously applied layers, still only partially set, will tend to redissolve and peel away from the ground. In this egg-tempera portrait, the form has been created by many parallel strokes of color