In perfumery, a fixative is a natural or synthetic substance used to reduce the evaporation rate and improve stability when added to more volatile components. This allows the final product to last longer while keeping its original fragrance. Fixatives are indispensable commodities to the perfume industry. Some examples of fixatives are ambergris, sandalwood, musk, vetiver, orris root, and bergamot orange. In some instances, such as soapmaking, castor oil, may be used. Natural fixatives usually have a fragrance considered a base note in perfumery terms, reflecting their low volatility.