Yes, you can use oil, such as linseed oil, to blend oil pastels.
Oil pastels are pigment mixed with a non-drying oil and wax binder. Because of this oil-based composition, using oil can help to soften and blend the colors together, creating smoother transitions and effects. Other solvents, like paint thinner, can also be used for blending, though linseed oil is specifically mentioned as an option. Using oil or solvents changes the consistency of the oil pastel, allowing for techniques like glazing or creating washes.
