Oil paint is a type of slow-dryingpaint that consists of particles ofpigment suspended in adrying oil, commonlylinseed oil. Oil paint also has practical advantages over other paints, mainly because it is waterproof.
The earliest surviving examples of oil paint have been found in Asia from as early as the 7th century AD, in examples ofBuddhist paintings inAfghanistan. Oil-based paints made their way to Europe by the 12th century and were used for simple decoration, mostly on wood. Common modern applications of oil paint are in finishing and protection ofwood inbuildings and exposed metal structures such as ships and bridges. Its hard-wearing properties and luminous colors make it desirable for bothinterior and exterior use on wood, metal and fabric. Due to its slow-drying properties, it has recently been used inpaint-on-glass animation. The thickness of the coat has considerable bearing on the time required for drying: thin coats of oil paint dry relatively quickly.
The viscosity of the paint may be modified by the addition of a solvent such asturpentine orwhite spirit, andvarnish may be added to increase theglossiness of the dried oil paint film. The addition of oil oralkyd medium can also be used to modify the viscosity and drying time of oil paint.
The technical history of the introduction and development of oil paint, and the date of introduction of various additives (driers, thinners) is still — despite intense research since the mid-19th century - not well understood. Incorrect theories and information are common, especially in sources written before 1952.[1] Until 1991 nothing was known about the organic aspect of cave paintings from thePaleolithic era. Many assumptions were made about thechemistry of the binders. Well-known Dutch-American artistWillem de Kooning is known for saying "Flesh is the reason oil paint was invented".[2]
The oldest known oil paintings are Buddhist murals createdc. 650 AD. The works are located in cave-like rooms carved from the cliffs of Afghanistan'sBamiyan Valley, "using walnut, poppy seed oils, Linseed oil and castor oil."[3] In some regions, this technique is referred to as thedrying oil technique.
Though the ancient Mediterranean civilizations ofGreece,Rome, andEgypt usedvegetable oils, there is little evidence to indicate their use asmedia in painting. Indeed,linseed oil was not used as a medium because of its tendency to dry very slowly, darken, and crack, unlikemastic andwax (the latter of which was used inencaustic painting).
Greek writers such asAetius Amidenus recorded recipes involving the use ofoils for drying, such aswalnut,poppy,hempseed,pine nut,castor, and linseed. When thickened, the oils became resinous and could be used asvarnish to seal and protect paintings from water. Additionally, when yellowpigment was added to oil, it could be spread overtin foil as a less expensive alternative togold leaf.
Christianmonks were aware of these ancient books and used the techniques in their own artworks.Theophilus Presbyter, a 12th-century German monk, recommended linseed oil but advocated against the use ofolive oil due to its long drying time. Oil paint was mainly used as it is today in house decoration, as a tough waterproof cover for exposed woodwork, especially outdoors.
In the 13th century, oil was used to detailtempera paintings. In the 14th century,Cennino Cennini described a painting technique utilizingtempera painting covered by light layers of oil. The slow-drying properties oforganic oils were commonly known to early painters. However, the difficulty in acquiring and working the materials meant that they were rarely used (and indeed the slow drying was seen as a disadvantage[4]).
As the public preference for naturalism increased, the quick-dryingtempera paints became insufficient to achieve the very detailed and precise effects that oil could achieve. TheEarly Netherlandish painting of the 15th century saw the rise ofpanel painting purely in oils, oroil painting, or works combining tempera and oil painting, and by the 16th-century easel painting in pure oils had become the norm. The claim byVasari thatJan van Eyck "invented" oil painting is not correct, but van Eyck'suse of oil paint achieved novel results in terms of precise detail and mixing colorswet-on-wet. Van Eyck's mixture may have consisted of piled glass,calcined bones, and mineral pigments boiled in linseed oil until they reached aviscous state—or he may have simply used sun-thickened oils (slightly oxidized by Sun exposure)[citation needed].
The Flemish-trained or influencedAntonello da Messina, whom Vasari wrongly credited with the introduction of oil paint to Italy,[5] does seem to have improved the formula by addinglitharge, or lead (II) oxide. The new mixture had a honey-like consistency and better drying properties (drying evenly without cracking). This mixture was known asoglio cotto—"cooked oil."Leonardo da Vinci later improved these techniques by cooking the mixture at a very low temperature and adding 5 to 10%beeswax, which prevented the darkening of the paint.Giorgione,Titian, andTintoretto each may have altered this recipe for their own purposes.
The paint tube was invented in 1841 by the portrait painterJohn Goffe Rand,[6] supersedingpig bladders and glass syringes[7] as the primary tool of paint transport. Artists, or their assistants, previously ground each pigment by hand, carefully mixing the binding oil in the proper proportions. Paints could now be produced in bulk and sold in tin tubes with a cap. The cap could be screwed back on and the paints preserved for future use, providing flexibility and efficiency to painting outdoors. The manufactured paints had a balanced consistency that the artist could thin with oil, turpentine, or other mediums.
Paint in tubes also changed the way some artists approached painting. The artistPierre-Auguste Renoir said, "Without tubes of paint, there would have been noimpressionism." For the impressionists, tubed paints offered an easily accessible variety of colors for theirplein air palettes, motivating them to make spontaneous color choices.
Traditional oil paints require an oil that always hardens, forming a stable, impermeable film. Such oils are called causative, ordrying, oils, and are characterized by high levels ofpolyunsaturatedfatty acids. One common measure of the causative property of oils isiodine number, the number of grams ofiodine one hundred grams of oil can absorb. Oils with an iodine number greater than 130 are considered drying, those with an iodine number of 115–130 are semi-drying, and those with an iodine number of less than 115 are non-drying. Linseed oil, the most prevalent vehicle for artists' oil paints, is a drying oil.
When exposed to air, oils do not undergo anevaporation process like water does. Instead, they dry semisolid byoxidation causingpolymerization. The rate of this process can be very slow, depending on the oil.
The advantage of the slow-drying quality of oil paint is that an artist can develop a painting gradually. Earlier media such as egg tempera dried quickly, which prevented the artist from making changes or corrections. With oil-based paints, revising was comparatively easy. The disadvantage is that a painting might take months or years to finish, which might disappoint an anxious patron. Oil paints blend well with each other, making subtle variations of color possible as well as creating many details of light and shadow. Oil paints can be diluted with turpentine or other thinning agents, which artists take advantage of to paint in layers.
There is also another kind of oil paint that is water-mixable, making the cleaning and using process easier and less toxic.
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The earliest and still most commonly used vehicle islinseed oil, pressed from theseed of theflax plant. Modern processes use heat or steam to produce refined varieties of oil with fewer impurities, but many artists prefer cold-pressed oils.[8] Other vegetable oils such ashemp,poppy seed,walnut,sunflower,safflower, andsoybean oils may be used as alternatives to linseed oil for a variety of reasons. For example, safflower and poppy oils are paler than linseed oil and allow for more vibrant whites straight from the tube.
Once the oil is extracted,additives such asLiquin are sometimes used to modify its chemical properties. In this way, the paint can be made to dry more quickly (if that is desired), or to have varying levels ofgloss. Modern oils paints can, therefore, have complex chemical structures; for example, affecting resistance toUV. By hand, the process involves first mixing the paint pigment with the linseed oil to a crumbly mass on a glass or marble slab. Then, a small amount at a time is ground between the slab and a glassmuller (a round, flat-bottomed glass instrument with a handgrip). Pigment and oil are ground together 'with patience' until a smooth, ultra-fine paste is achieved. This paste is then placed into jars or metal paint tubes and labeled. Modern industrial production usesmill rollers to grind pigment and oil together into a paste.
The color of oil paint is derived from small particles of colored pigments mixed with the carrier, the oil. Common pigment types include mineral salts such as white oxides:zinc oxide,titanium dioxide, and the red to yellowcadmium pigments. Another class consists ofearth types, the main ones beingochre,sienna andumber. Still another group of pigments comes from living organisms, such asmadder root.Synthetic Organic and inorganic pigments have been introduced since the nineteenth century. Natural pigments have the advantage of being well understood through centuries of use, but synthetics have greatly increased the spectrum of available colors, and many have a high level oflightfastness.
When oil paint was first introduced in the arts, basically the same limited range of available pigments were used that had already been applied in tempera: yellow ochre,umber,lead-tin-yellow,vermilion,kermes,azurite,ultramarine,verdigris,lamp black andlead white. These pigments strongly varied in price, transparency, and lightfastness. They included both inorganic and organic substances, the latter often being far less permanent. The painter bought them from specialized traders, "color men", and let his apprentices grind them with oil in his studio to obtain paint of the desiredviscosity.
During theAge of Discovery, new pigments became known in Europe, most of the organic and earthy type, such asIndian yellow. In the eighteenth century, the developing science ofchemistry expanded the range of pigments, which led to the discovery ofPrussian blue andcobalt blue. In the nineteenth century, synthetic ultramarine was introduced,zinc white,viridian,chrome yellow, cadmium colours,aureolin, syntheticalizarin andcerulean blue. In the twentieth century, mass production started oftitanium white and a new range of lightfast synthetic organic pigments, such asarylide yellow,phthalocyanine andquinacridone. Though having mainly an industrial application, these pigments by the twenty-first century had largely replaced traditional types in artistic oil paint also.
Many of the historical pigments were dangerous, and many pigments still in use are highly toxic. Some of the most poisonous pigments, such asParis green (copper(II) acetoarsenite) andorpiment (arsenic sulfide), have fallen from use.
Many pigments are toxic to some degree. Commonly used reds and yellows are produced usingcadmium, andvermilion red uses natural or synthetic mercuric sulfide orcinnabar.Flake white and Cremnitz white are made with basiclead carbonate. Some intense blue colors, includingcobalt blue andcerulean blue, are made with cobalt compounds. Some varieties of cobalt violet are made withcobalt arsenate.
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