manufacture often differs slightly from normal bath soap in that both potassium hydroxide and sodium hydroxide may be used as saponification agents. Sodium hydroxide creates a harder soap such as is used in pucks, where potassium hydroxide facilitates creation of a softer soap which loads on the brush more easily. Historically, tallow has been a popular ingredient in shaving soaps and is still in use in some traditional products. Palm oil is frequently used as a substitute for tallow where animal fats are not desired. Other oils such as coconut oil are commonly used. Component fatty acids such as stearic acid are also used in shaving soaps for the properties which they contribute; stearic acid contributes to a more stable dense lather. Advantages and disadvantages The primary advantages of shaving soap over aerosol shaving creams is the additional hydration provided by shaving soaps. Shaving soaps are also approved by the Transportation Security Administration and other airport security agencies as permitted in carry-on luggage. There is furthermore little risk of accidental discharge of the product during transport. The principal disadvantages of shaving soap is lack of convenience and space. Creating the lather and preparing the face is more time-consuming than with other shaving creams. In addition, use of a shaving mug and optionally a lather bowl, consumes more space and takes more time than most shaving creams do. Shaving soaps typically cost more initially, when the shaving mug and soap is purchased. These costs can be significantly reduced by using mugs and bowls found in the kitchen, or purchased for a small amount at resale stores. Even though shaving soaps may cost more initially when buying the soap and equipment, over a longer period of time, shaving soaps are comparable in cost, or even cheaper than many shaving creams. Furthermore, shaving soaps have less ecological impact with respect to aerosol shaving creams. See also Aftershave Barber Bay rum Beard Burma-Shave Colognes Head shaving Leg shaving List of cleaning products Razors Saltwater soap Shaving cream Straight razor References Bibliography Soaps Shaving implements