The working principles of common oil painting media are as follows:
Drying oil: Drying oil is the foundation of oil painting media. Its working principle is based on the chemical reaction between the fatty acids in the oil and the oxygen atoms in the air, thereby achieving drying. For instance, flaxseed oil has a relatively short drying time and a tough film formation. It is the main oil used in oil paints. After processing, it can be made into color carriers and various painting media. Poppy oil is light in color and odorless, with a relatively slow drying time. It is suitable for long-term wet painting and is often used as a color carrier for light or white pigments. The drying time and yellowing degree of walnut oil are between those of flaxseed oil and poppy oil. The cooked oil made from walnut oil can be used as an excellent medium and is also a good material for oil-based base seasonings. Red flower oil originated in India. It is used as a carrier for oil paints and is not prone to yellowing. Its performance is similar to that of poppy oil.
Diluent: The principle of the diluent lies in its volatility. It can quickly evaporate and carry away some components in the pigment, thereby reducing the viscosity of the pigment and facilitating the painter’s color mixing and painting operations. Turpentine is a common diluent solvent. It has strong volatility, leaves little residue, is colorless and transparent, and evaporates thoroughly. It can be used to dilute tinted oils and oil paints, and is also an indispensable material for homemade varnishes and various tinted oils.
Resin: The main principle of the function of resin in oil painting media is to enhance the firmness, flexibility and gloss of the paint layer, while providing a certain protective effect. Resin solutions such as Damar oil and Damar varnish can be used to prepare media agents or as varnishes. Mati varnish is flexible, transparent, turns yellow slowly and is easy to remove during repair. It is one of the better varnishes on the market at present. Dama varnish is firm and economically priced, but it is prone to yellowing and difficult to repair.
Desiccant: The working principle of a desiccant is to accelerate the oxidation process of drying oil, thereby shortening the drying time of pigments. Different types of pigments have different effects on the drying speed of oil. To ensure that oil paints can dry within a certain period of time and that the drying times of various colors are relatively consistent, desiccants need to be added to the pigments to adjust the drying speed. However, excessive use may cause the pigment to crack. Generally, the proportion of desiccant added to the medium should not exceed 2-3% of the oil.