Drying oil in the context of "Oil paint"

Oil painting is a painting method involving the procedure of painting with pigments combined with a drying oil as the binder. It has been the most common technique for artistic painting on canvas, wood panel, or copper for several centuries. The advantages of oil for painting images include "greater flexibility, richer and denser color, the use of layers, and a wider range from light to dark".

The oldest known oil paintings were created by Buddhist artists in Afghanistan, and date back to the 7th century AD. Oil paint was later developed by Europeans for painting statues and woodwork from at least the 12th century, but its common use for painted images began with Early Netherlandish painting in Northern Europe, and by the height of the Renaissance, oil painting techniques had almost completely replaced the use of egg tempera paints for panel paintings in most of Europe, though not for Orthodox icons or wall paintings, where tempera and fresco, respectively, remained the usual choice.

Soybean oil (British English: soyabean oil) is a vegetable oil extracted from soybean (Glycine max) legumes. It is one of the most widely consumed cooking oils and the second most consumed vegetable oil. As a drying oil, processed soybean oil is also used as a base for printing inks (soy ink) and oil paints.

Tung oil or China wood oil is a drying oil obtained by pressing the seed from the nut of the tung tree (Vernicia fordii). Tung oil hardens upon exposure to air (through polymerization), and the resulting coating is transparent and has a deep, almost wet look. Used mostly for finishing and protecting wood, after numerous coats, the finish can even look plastic-like. Related drying oils include linseed, safflower, poppy, and soybean oils. Raw tung oil tends to dry to a fine, wrinkled finish. This property was used to make wrinkle finishes, usually by adding excess cobalt drier. To prevent wrinkling, the oil is heated to gas-proof it (also known as "boiled").

"Tung oil finish" is often used by paint and varnish manufacturers as a generic name for any wood-finishing product that contains the real tung oil or provides a finish that resembles the finish obtained with tung oil.

A non-drying oil is an oil which does not harden and remains liquid when it is exposed to air. This is as opposed to a drying oil, which hardens (through polymerization) completely, or a semi-drying oil, which partially hardens. Oils with an iodine number of less than 115 are considered non-drying.

Autoxidation (sometimes auto-oxidation) refers to oxidations brought about by reactions with oxygen at normal temperatures, without the intervention of flame or electric spark. The term is usually used to describe the gradual degradation of organic compounds in air at ambient temperatures. Many common phenomena can be attributed to autoxidation, such as food going rancid, the 'drying' of varnishes and paints, and the perishing of rubber. It is also an important concept in both industrial chemistry and biology. Autoxidation is therefore a fairly broad term and can encompass examples of photooxygenation and catalytic oxidation.

The common mechanism is a free radical chain reaction, where the addition of oxygen gives rise to hydroperoxides and their associated peroxy radicals (ROO•). Typically, an induction period is seen at the start where there is little activity; this is followed by a gradually accelerating take-up of oxygen, giving an autocatalytic reaction which can only be kept in check by the use of antioxidants. Unsaturated compounds are the most strongly affected but many organic materials will oxidise in this way given time.