SHAVING CREAMPR EPARATIONS
Throughout recorded history, the act of removing hair from various parts of the body via shaving with razors has been associated with such factors as cleanliness and hygiene, social rank, military dominance, fashion trendiness, and vanity. Early shaving preparations often included soaps, oils, or herbal treatments such as cherry laurel water. Most modern shaving preparations are designed to lubricate the skin and allow the cutting blade to cut the protruding hair shaft (and not the surrounding skin), to moisten and soften hair to ease cutting capabilities, and to serve as a demarcation of where shaving has already occurred, thereby preventing skin irritation with repeated razor strokes.
While the use of water alone can soften hair, the addition of a fatty acid salt (i.e., soap) improves the performance of water as a shaving aid by creating a film on the skin. This film created by shaving soaps allows the blade to slide with decreased resistance along the outer epidermal skin surface without cutting into the vascular (blood vessel-possessing) deeper dermal skin layer. In general, soap results from the treatment of natural oils (e.g., animal tallow, fish oil, or sunflower oil, vegetable oils such as corn oil, soybean oil, olive oil, palm oil, coconut oil) and fats with an alkaline solution followed by neutralization. This process allows for the production of free fatty acids and glycerine via hydrolysis of the fatty acid esters. The texture of the soap is dependent on the fatty acid chain length and the degree of saturation. For example, whereas “hard” soaps result from the use of saturated fatty acids (e.g., stearic acid, pal- mitic acid), “soft” soaps result from the use of unsaturated fatty acids (e.g., linoleic acid, oleic acid) during formulation. In addition, although longer- chain fatty acids contribute to the stability of the foam, shorter-chain fatty acids (e.g., twelve carbons) allow for fast foam formation associated with small bubbles. Shaving soaps were first commercially manufactured in the 1830s and often were a mixture of tallow, stearic acid, potash, and caustic soda formed into a bar. Toward the 1940s, most shaving soaps were formulated to be used with a brush and mug. While some modern shaving soap preparations are nonlathering (only providing lubrication and moisture), foaming shaving soaps are typically designed so that me- chanical agitation with the hands or use of the brush-and-mug method creates a foam that is used to coat the skin and provide efficient hydration. Standard modern foaming shaving soaps consist of fatty acids (e.g., stearic acid, palmitic acid, potassium myristate, sodium myristate), oils (e.g., coconut oil, palm kernel oil, corn oil), emollients (e.g., glycerin), and humectants (e.g., purified water), frequently formulated with alkaline chemical neutralizers (e.g., sodium hydroxide, potassium hydroxide), fragrance, and preservatives.
In the late 1940s, commercialization of aerosol shaving products led to the development of a variety of chemical formulations beyond a soap and water base. Aerosol foams consist typically of a potassium or sodium salt fatty acid mixture within a liquid soap base that foams upon application. Included are additional materials such as skin cleansers and antiseptics (e.g., triclosan, sodium lauryl sulfate), product thickeners (e.g., acrylate copolymers, cellulose polymer, carrageenan, hydroxyethylcellu- lose), surfactant/fatty acid neutralizers (e.g., triethanolamine), lubricants and emollients (e.g., lanolin, allantoin, sorbitol), hair and skin softeners/ hydrating humectants (e.g., propylene glycol, glycerin, PEG compounds), and skin conditioners (e.g., Aloe vera gel, sodium cocoyl isothionate, vi- tamin E acetate, panthenol). In addition, herbal extracts (e.g., lime, lady’s mantle, soapwort, peppermint, horsetail, watercress, lemongrass, sage, golden seal, orange flower), preservatives (e.g., BHT, DMDM hydantoin, quaternium-15, methylparaben, propylparaben, sodium benzoate), color- ing pigments, and fragrance are often added to improve product quality and purity. Overall, these ingredients are combined in three-piece metal cans and applied to the skin with the use of propellants that include isobutane, propane, pentane, butane, and isopentane.
Specialized postfoaming shave gels, first developed in the early 1970s, frequently possess soap bases similar to traditional aerosol shaving for- mulations but also contain a polymer and other surfactant materials in the presence of selected hydrocarbons, which allows for the creation of a clear gel structure. Common ingredients in these products include deionized water, a fatty acid (palmitic acid)/triethanolamine salt mix- ture, fatty acid esters, a pentane/isobutane postfoaming mix, and a cellulose polymer. Mechanical movement of the gel over the skin surface creates a dense foam, providing additional lubrication and protection preferred by many consumers over traditional shaving foams.
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