The Creation of Adam, detail of the ceiling fresco by Michelangelo, 1508–12; in the Sistine Chapel, Vatican City.SuperStock
Sgraffito
Sgraffito (Italian graffiare, “to scratch”) is a form of fresco painting for exterior walls. A rough plaster undercoat is followed by thin plaster layers, each stained with a different lime-fast colour. These coats are covered by a fine-grain mortar finishing surface. The plaster is then engraved with knives and gouges at different levels to reveal the various coloured layers beneath. The sintered-lime process binds the colours. The surface of modern sgraffito frescoes is often enriched with textures made by impressing nails and machine parts, combined with mosaics of stone, glass, plastic, and metal tesserae.
Březnice Château: sgraffitoDetail of Renaissance sgraffito on the walls of the Březnice Château, Czech Republic.Miaow Miaow
Sgraffito has been a traditional folk art in Europe since the Middle Ages and was practiced as a fine art in 13th-century Germany. It was revived in updated and modified ways by 20th-century artists such as Max Ernst and Jean Dubuffet. Oil
Oil paints are made by mixing dry pigment powder with refined linseed oil to a paste, which is then milled in order to disperse the pigment particles throughout the oil vehicle. According to the 1st-century Roman scholar Pliny the Elder, whose writings the Flemish painters Hubert and Jan van Eyck are thought to have studied, the Romans used oil colours for shield painting. The earliest use of oil as a fine-art medium is generally attributed to 15th-century European painters, such as Giovanni Bellini and the van Eycks, who glazed oil colour over a glue-tempera underpainting. It is also thought probable, however, that medieval manuscript illuminators had been using oil glazes in order to achieve greater depth of colour and more subtle tonal transitions than their tempera medium allowed.
Oils have been used on linen, burlap, cotton, wood, hide, rock, stone, concrete, paper, cardboard, aluminum, copper, plywood, and processed boards, such as masonite, pressed wood, and hardboard. The surface of rigid panels is traditionally prepared with gesso and that of canvas with one or more coats of white acrylic resin emulsion or with a coat of animal glue followed by thin layers of white-lead oil primer. Oil paints can be applied undiluted to these prepared surfaces or can be used thinned with pure gum turpentine or its substitute, white mineral spirit. The colours are slow drying; the safest dryer to speed the process is cobalt siccative.
Hopkins, Frances Anne: Canoe Manned by Voyageurs Passing a WaterfallCanoe Manned by Voyageurs Passing a Waterfall, oil on canvas by Frances Anne Hopkins, 1869; in Library and Archives Canada, Ottawa, Ontario.Library and Archives Canada (00001 1989-401)
An oil glaze is a transparent wash of pigment, traditionally thinned with an oleoresin or with stand oil (a concentrate of linseed oil). Glazes can be used to create deep, glowing shadows and to bring contrasted colours into closer harmony beneath a unifying tinted film. Scumbling is the technique of scrubbing an undiluted, opaque, and generally pale pigment across others for special textural effects or to raise the key of a dark-coloured area.
Hog-bristle brushes are used for much of the painting, with pointed, red sable-hair brushes generally preferred for outlines and fine details. Oils, however, are the most plastic and responsive of all painting mediums and can be handled with all manner of tools. The later works of Titian and Rembrandt, for example, appear to have been executed with thumbs, fingers, rags, spatulas, and brush handles. With these and other unconventional tools and techniques, oil painters create pigment textures ranging from delicate tonal modulations to unvarying, mechanical finishes and from clotted, impasto ridges of paint to barely perceptible stains.
Adam and Eve in the Garden of Eden, oil painting by Titian, c. 1550; in the Prado, Madrid.SCALA/Art Resource, New York
The tempera-underpainting-oil-glaze technique was practiced into the 17th century. Artists such as Titian, El Greco, Rubens, and Diego Velázquez, however, used oil pigments alone and, employing a method similar to pastel painting, applied them directly to the brownish ground with which they had tinted the white priming. Contours and shadows were stained in streaks and washes of diluted paint, while lighter areas were created with dry, opaque scumbles, the tinted ground meanwhile providing the halftones and often remaining untouched for passages of local or reflected colour in the completed picture. This use of oil paint was particularly suited to expressing atmospheric effects and to creating chiaroscuro, or light and dark, patterns. It also encouraged a bravura handling of paint, where stabs, flourishes, lifts, and pressures of the brush economically described the most subtle changes of form, texture, and colour according to the influence exerted by the tinted ground through the varying thicknesses of overlaid pigment. This method was still practiced by the 19th-century painters, such as John Constable, J.M.W. Turner, Eugène Delacroix, and Honoré Daumier. The Impressionists, however, found the luminosity of a brilliant white ground essential to the alla prima technique with which they represented the colour intensities and shifting lights of their plein air (open air) subjects. Most oil paintings since then have been executed on white surfaces.
The rapid deterioration of Leonardo’s 15th-century Last Supper (last restored 1978–99), which was painted in oils on plaster, may have deterred later artists from using the medium directly on a wall surface. The likelihood of eventual warping also prohibited using the large number of braced wood panels required to make an alternative support for an extensive mural painting in oils. Because canvas can be woven to any length and because an oil-painted surface is elastic, mural paintings could be executed in the studio and rolled and restretched on a wooden framework at the site or marouflaged (fastened with an adhesive) directly onto a wall surface. In addition to the immense studio canvases painted for particular sites by artists such as Jacopo Tintoretto, Paolo Veronese, Delacroix, Pierre-Cécile Puvis de Chavannes, and Claude Monet, the use of canvas has made it possible for mural-size, modern oil paintings to be transported for exhibition to all parts of the world.
Leonardo da Vinci: Last SupperLast Supper, wall painting by Leonardo da Vinci, c. 1495–98, before the restoration completed in 1999; in Santa Maria delle Grazie, Milan.SuperStock
The tractable nature of the oil medium has sometimes encouraged slipshod craftsmanship. Working over partly dry pigment or priming may produce a wrinkled surface. The excessive use of oil as a vehicle causes colours to yellow and darken, while cracking, blooming, powdering, and flaking can result from poor priming, overthinning with turpentine, or the use of varnish dryers and other spirits. Colour changes may also occur through the use of chemically incompatible pigment mixtures or from the fading of fugitive synthetic hues, such as crimson lakes, the brilliant red pigment favoured by Pierre-Auguste Renoir. Watercolour