Anatomy of a Shaving Cream

Have you ever read the ingredients on the label of your shaving soap or cream and wondered what they are and what they do? In every shaving cream formulation, each ingredient plays a role. While some ingredients are essential, others only have a minor effect. The performance of the cream serves as the ultimate test for the formulation and indicates whether the correct blend of ingredients and concentrations has been used. High tier shaving creams have a common structure that includes carefully selected ingredients that have been optimized for years. Deviations from these general guidelines results in poorer performance. In this article, the role of the most common ingredients found in high performance shaving creams and their effect on performance will be described.
The following is a typical ingredient list on a high end shaving cream: aqua (water), stearic acid, myristic acid, potassium hydroxide, coconut acid, glycerin, triethanolamine, parfum (fragrance) and sodium hydroxide. The word cocoate, usually preceded by sodium or potassium, may be found replacing coconut acid to indicate that saponification has occurred. Saponification literally means “soap making” (from the root word, “sapo”, which is Latin for soap), and is a chemical reaction used to produce fatty acids from triglycerides. Triglyceride consist of three fatty acid molecules joined to a glycerin molecule, which is also released during saponification. Triglycerides are the preferred molecules used by living organisms to store fats and their constitution is unique for a particular species but varies from one species to another.

In addition, shaving creams often contain other ingredients including: botanicals, essential oil derivatives (e. g. citral, farnesol, geraniol, geranial, myrcene, limonene, linalool, etc.), chelators, preservatives and other chemicals. Besides modulating performance, these ingredients can add antiseptic qualities, serve as skin toners, increase shelf life, etc. but more importantly, they make each formulation unique. The focus of this article will be the core ingredients that define the scaffold found in high end shaving creams:

Aqua: water
Stearic acid: saturated fatty acid
Myristic acid: saturated fatty acid
Potassium hydroxide: inorganic base
Sodium hydroxide: inorganic base
Coconut acid: triglyceride
Glycerin: polyol or sugar alcohol
Triethanolamine: organic base

Aqua: Water is a solvent that is used to dissolve certain ingredients in the shaving cream and serves as the matrix in which air is trapped when lather (foam) is formed. Water is also used as a spreading agent that distributes other ingredients evenly and gives shaving creams a soft texture. In the lather, water contributes to keep the hair moist during the shave and is responsible for the glide or slip of the lather. When water concentration in lather is not optimal, the performance of the lather is subpar.

Stearic acid: Stearic acid is a saturated fatty acid and a surfactant (literally, an amphiphilic,“surface acting”, chemical that lowers surface tension at the interface between molecules or groups of molecules that do not mix well) that has excellent emulsifying and lather stabilizing properties. It is also used as an emollient and thickening agent. Stearic acid is often used as inorganic or organic salt or as an ester.

Myristic acid: Another saturated member of the fatty acid family and is also used in shaving creams for its surfactant and emulsifying properties. Myristic acid forms intermediate bubble sizes that result in faster foaming and reduced mechanical stability.

Coconut acid: Coconut acid is a triglyceride extracted from the plant Cocos nucifera or coconut palm. It is commonly known as coconut oil. When saponified, coconut acid is used in shaving cream as a source of surfactants and cleansing agents.. Saponification of coconut oil produces a mixture rich in saturated fatty acids that include (listed in order of abundance): lauric, myristic, palmitic and stearic acids and a small proportion of unsaturated fatty acids. Unsaturated fatty acids can be completely removed from formulation and recently have been linked to comedogenesis (a type of acne caused by cosmetics). In high concentration, unsaturated fatty acids can oxidize over time and decrease shelf life. Glycerin is a by-product of the saponification reaction. Coconut acid also is used to adjust pH, and its derivatives are used as emollients.

Sodium and Potassium hydroxides: These are strong inorganic bases that are used to saponify triglycerides. Inorganic bases are also used to make fatty acids more soluble in water. Typically, fatty acids are found in shaving creams as sodium and potassium salts. The ratio in which these bases are used determines the consistency of the shaving cream for a given water and fatty acid composition. These are highly alkaline and are used to adjust pH. Sodium hydroxide is also called caustic soda or lye. The common name for potassium hydroxide is potash.

Glycerin: Glycerin, or more correctly, glycerol, belongs to the sugar alcohol family. Gycerol does not have surface activity and cannot form lather. Glycerol can retain water, thus increasing lather density and stability. For this reason, glycerol is also used as a humectant. Glycerol also increases the viscosity of water-glycerol solutions, affecting the glide of the lather. Although its effect on deeper layers of the skin remains under investigation, there is very little doubt that hydrated glycerin has a beneficial effect when applied to the outer-most layer of the skin (the stratum corneum).

Triethanolamine: Triethanolamine or TEA is an organic base used primarily as emulsifier and surfactant. It is also used in shaving creams to neutralize the pH of fatty acids and to solubilize oils and other ingredients that have poor solubility in water. Triethanolamine use has been reduced in recent times because of growing safety and health concerns due to its suspected role as irritant and carcinogen and its ability to react with other chemicals to form carcinogenic nitrosamines. Some studies have linked TEA to contact dermatitis and allergies. TEA is currently under review in USA, UK and European countries. Triethanolamine can be completely removed from shaving cream formulations without any loss of performance.

Determining performance from ingredient lists is often complicated because the actual contents of the product are not listed. Furthermore, ingredient lists do not include the concentration of each ingredient or their purity. This can also be problematic when troubleshooting allergic reactions. It is important to realize that the process of selecting shaving products is not an exact science and several factors, including glycerin content, scent and other additives can modulate performance. Personal preference, allergies, etc. can be important factors in the selection process. However, shaving creams that use the scaffold covered here rank among the best in the market and are known for their unsurpassed performance.

Al.