Glossary of Art Terms - O

Oil Paint

Oil paint is a type of slow-drying paint consisting of small pigment particles suspended in a drying oil. Oil paints have been used in England as early as the 13th century for simple decoration, but were not widely adopted for artistic purposes until the 15th century. The most common modern application of oil paint is domestic, where its hard-wearing properties and luminous colors make it desirable for both interior and exterior use. Its slow-drying properties have recently been used in paint-on-glass animation.

Oil Painting

Oil painting is the process of painting with pigments that bound with medium of drying oil — especially in early modern Europe, linseed oil. Often an oil, such as linseed was boiled with a resin such as pine resin or even frankincense, these were called 'varnishes' and were prized for their body and gloss. Other oils occasionally used include poppyseed oil, walnut oil, and safflower oil. These oils give various properties to the oil paint, such as less yellowing or different drying times. Certain differences are also visible in the sheen of the paints depending on the oil. Painters often use different oils in the same painting depending on specific pigments and effects desired. The paints themselves also develop a particular feel depending on the media. A basic rule of oil paint application is 'fat over lean.' This means that each additional layer of paint should be a bit oilier than the layer below, to allow proper drying. Traditional oil painting techniques often begin with paint mixed with turpentine or artist grade mineral spirits or other lean vehicles. As a painting gets additional layers, the paint must get oilier (leaner to fatter) or the final painting will crack and peel. There are many other painting media that can be used in oil painting, including cold wax, resins, and varnishes. These additional media can aid the painter in adjusting the translucency of the paint, the sheen of the paint, the density or 'body' of the paint, and the ability of the paint to hold or conceal the brushstroke. These variables are closely related to the expressive capacity of oil paint. When looking at original oil paintings, the various traits of oil paint allow one to sense the choices the artist made as they applied the paint. For the viewer, the paint is still, but for the artist, the oil paint is a liquid or semi-liquid and must be moved 'onto' the painting surface. Traditionally, moving paint was accomplished with paint brushes, but there are other methods, including the palette knife, the rag, and even directly from the paint tube. Oil paint remains wet longer than many other types of artists' materials, so a reality in many painter's studios is the removal of oil paint from the painting. This can be done with a rag and some turpentine for a certain time while the paint is wet, but after a while, the hardened layer must be scraped. Many oil paintings reveal evidence of such scraping on close inspection, particularly when the surface itself is examined. Oil paint dries by oxidation, not evaporation, and is usually dry to the touch in a day to two weeks. It is generally dry enough to be varnished in six months to a year. Art conservators do not consider an oil painting completely dry until it is 60 to 80 years old.

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Op Art

Op art, also known as optical art, is used to describe some paintings and other works of art which use optical illusions. Op art is also referred to as geometric abstraction and hard-edge abstraction, although the preferred term for it is perceptual abstraction. The term "Op" bears resemblance to the other popular movement of the 1960s, Pop Art though one can be certain such monikers were invoked for their catchiness and not for any stylistic similarities. (Plop art would be an example of another outgrowth from the term Pop art.) "Optical Art is a method of painting concerning the interaction between illusion and picture plane, between understanding and seeing."[1] Op art works are abstract, with many of the better known pieces made in only black and white. When the viewer looks at them, the impression is given of movement, hidden images, flashing and vibration, patterns, or alternatively, of swelling or warping.


Overpainting by definition must be done over some type of underpainting, in a system of working in layers. If the underpainting is like a base rhythm in music, then the overpainting is like the solo. The underpainting gives a context in which the paint-strokes of the overpainting become more resonant and powerful. When properly done, overpainting does not need to completely obscure the underpainting. It is precisely the interaction of the two that gives the most interesting effects. Overpainting was used extensively in many schools of art. Some of the most spectacular results can be seen in the work of Jan van Eyck. Unfortunately, it can be difficult to distinguish overpainting from underpainting in finished historical artworks in the absence of scientific tests. An example of overpainting can be seen in the contemporary still life painting of Hanneke van Oosterhout.

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