Vegetable and animal oils and derived products have been used for centuries as binders in varnishes and paints. Oil painting on wood was known in ancient times, but drying time was so long that this technique was not widespread. In the early medieval period, artists using pigments suspended in oils, preferably linseed oil, discovered that contamination with copper or lead decreased the drying time of paints and varnishes. This process was described by Aetius and Teofil the Monk.(1,2)
Pure unsaturated oils, even in favourable humidity and temperature conditions (20 °C, RH 50%), take a very long time to dry. The same oil boiled in a copper jar or in a vessel containing pieces of copper or lead metal dries over a relatively short amount of time. Varnishes were prepared in such a way in the Middle Ages. The content of metal derivatives, so called driers, promoted a rapid drying process. Further development of this technology led to oil paints used first by artists and later by the general public. In the beginning, paints were manufactured in small quantities, and the formulas were kept as family secrets. The first paint factories began during the European technical revolution in the eighteenth and nineteenth centuries. During that time some research was done and published in the technical literature. During the same time, the manufacturing method of driers based on the reaction of metal oxide with rosin acids was described. The same method is used today, and there are many descriptions of it.