From the manufacturer:
Concentrated Walnut/Alkyd Medium thins the color, accelerates drying, enhances adhesion between layers and increases surface sheen and flexibility while remaining essentially non-yellowing. Ideally suited for alla-prima and glaze applications. Walnut/Alkyd Medium is certified nontoxic.
Our walnut/alkyd medium is designed to augment the special nature of our oil color but is also completely compatible with other artists oil colors and mediums.