What is the most common binder used to mix oil paints?

Linseed oil is the most common binder used to mix oil paints due to its unique properties that enhance the paint's performance. As a drying oil, linseed oil polymerizes when exposed to air, leading to a firm and durable film when the paint dries. This quality not only allows for a rich, glistening finish but also contributes to the longevity of the artwork. In addition, linseed oil offers excellent flow and viscosity, allowing artists to achieve various textures and techniques in their work.

While turpentine is often used as a solvent for thinning oil paints and cleaning brushes, it does not serve as a binder. Similarly, vegetable oil, although it can act as a binder, is far less common in oil painting practice compared to linseed oil, primarily due to its slower drying time and lesser permanence. Hog hair brushes are tools used in the application of oil paints, but they do not relate to the composition of the paint itself. Hence, linseed oil remains the primary choice among artists for mixing with oil paints.