Substance of diverse chemical composition, less dense than and not mixable with water. In painting, where it is widely applied, oils may be classified as siccative (linseed, walnut, hemp and poppy seed oil), semi-siccative or semi-volatile (carnation and fish oil), non-drying and non-volatile (caster oil) and non-siccative volatile oils (essential oil, oil of turpentine, lavender oil or spike oil, refined oils from petroleum and hydrocarbons).