I noticed that someone was wondering if oiling out an oil painting with Walnut oil is safe. Absolutely! In fact the old dutch masters used walnut oil as a medium and their paintings are still in tact hundreds of years later. So yeah, it’s safe. Make sure your painting is one hundred percent dry. Pour some Walnut oil into a ceramic dish and using a soft brush, brush it on your painting and then with a soft lint-free cloth, gently wipe it all off again.