M. Graham Walnut Oil Mediums Walnut oil effectively removes color from artists’ brushes and is a natural vegetable oil that does not evaporate or remove essential oils from the artists’ brushes. The addition of walnut oil to color will slow drying, enhance flow and increase sheen. Our walnut oil medium is designed to augment the special nature of our oil color but is also completely compatible with other artists oil colors and mediums TWO PACK *Item label may have discoloration due to spilled oil when originally shipped. THESE HAVE BEEN UNOPENED AND HAVE NO LEAKS.