A paint essentially consists of three components: The binder, the solvent (also known as the thinner) and the pigment. The pigment’s particles can be thought of as a very fine, colored sand that is insoluble in water and most other solvents. Painted only with water or another solvent, said particles would break from the painted surface as soon as it evaporates. Therefore, a binder is needed to hold the pigment particles together and adhere them to the surface. A solvent is needed to dissolve or dilute the binder. For aqueous binders, water is the solvent; for oils, resins or waxes, non-aqueous solvents such as turpentine oil are necessary.
Each binder has advantages and disadvantages, possibilities and limitations. In the following, we present the binding agent known as oil.
The choice of binder - How to make paint
Oil as a binding agent
Oil painting is a technique developed over centuries. Its importance to the art of painting has never diminished, despite modern alternatives. On the contrary, many modern artists appreciate the qualities inherent to this tried & true painting process.
Not every oil is suitable for oil painting. Only non-volatile, drying oils are used to produce oil paint. These dry, more or less, quickly to a solid and non-sticky film. Traditionally, linseed oil, walnut oil and poppy oil are used in Europe.
Unlike aqueous binder systems such as acrylic paints or solvent-based varnishes and lacquers, oil paints do not dry by evaporation of the solvent, even though this is necessary to thin the paint. Oil paint drying is a chemical process in which the oil oxidizes by absorbing oxygen from the air. This process is slow and can take days, weeks, months or even years depending on the type of oil, additives, dilution, layer thickness, humidity and temperature.
Special features of oils:
- Cold-pressed oils are gently pressed at low temperatures and are more pure.
- Sun-thickened oils are lighter and thicker. The paint dries through quickly even in thicker layers.
- Oil varnish is the name given to oil thickened by boiling with the addition of siccatives or resins, thereby improving its drying properties.
Linseed oil
Linseed oil is obtained from the seed of the common flax Linum usitatissimum. The plant is cultivated and used in many countries, and the quality of the raw materials obtained also depends on the area of cultivation and the time of harvest. The linseed contains up to 40% linseed oil, which consists of about 60% linolenic acid, 15 (+/-5)% linoleic acid and oleic acid and less than 5% palmitic and stearic acid. In addition, the linseed oil also contains water and mucilage. Fresh linseed oil is light to dark yellow and loses its cloudiness through filtration or by leaving it standing.Walnut oil
Walnut oil is obtained from the shelled kernels of the walnut tree Juglans regia. The properties of walnut oil, both in terms of drying and yellowing, are between those of linseed oil and poppy oil. It is recommended for the use of lighter colors. Walnut oil consists of 60% linoleic acid, 15% linolenic acid and 15-20% oleic acid. It contains less than 10% palmitic acid and less than 5% stearic acid.Poppy oil
Poppy oil dries slower than linseed oil and walnut oil and the paint film remains softer, but the oil is least prone to yellowing. The poppy oil consists of 60-70% linoleic acid, 10-20% oleic acid, about 10% palimitic acid and usually less than 3% stearic acid and linolenic acid.
Caution: Sometimes dried poppy oil layers soften and become liquid again!
