Typically a mixture of different surfactants is used. Of the anionics, soap is not a common deliberate constituent of bath foam preparations because they react rapidly with "hardness" cations in water to produce lime soaps, which are anti-foams. Usually one or more ingredients is primarily a foam stabilizer—a substance which retards the breakage of foams; these may themselves be surfactants or film-stabilizing polymers. Some surfactants used in foaming preparations may have a combination of foam-producing and foam-stabilizing properties. Surfactants used in bath foam preparations may also be included for primarily non-foaming purposes: solubilization of other components in the manufacturing of a liquid product, or lime soap dispersion to prevent bathtub ring when used with soap.