Grumbacher Poppyseed Oil is a purified, non-yellowing oil painting medium. When mixed with oil colors, it slows their drying rate, allowing ample time for blending and other wet-into-wet techniques. It also makes colors smoother, improves their flow, and helps level out brushstrokes. It may be diluted with Grumtine, pure gum spirits of turpentine, or odorless paint thinner.