Which binder is most commonly used for oil paints?

Linseed oil is the most commonly used binder for oil paints for several reasons. It is derived from the seeds of the flax plant, and its properties lend themselves well to the creation of oil paints. Linseed oil has a slow drying time, which allows artists to work with their paint longer and blend colors effectively. This characteristic is particularly valuable in oil painting, where layering and subtle variations in color are often crucial to achieving the desired effects. Additionally, linseed oil enhances the luminosity of the colors, giving oil paintings their characteristic depth and richness.

In contrast, water is not suitable as a binder for traditional oil paints as oil and water do not mix, and using water can lead to undesirable results. Acrylic polymer is used in acrylic paints, not oil paints, and does not have the same properties as linseed oil for binding pigments in an oil medium. Beeswax, while used in some painting techniques and mixed media, does not serve as a common binder for oil paints. It can be used to create encaustic paintings rather than traditional oil paints. Thus, linseed oil is the correct answer as it is specifically designed for use in oil painting, providing the right balance of workability, drying time, and finish.