Considering hair styling, what could be more natural than simply combing or brushing hair? Or setting hair after shampooing and conditioning so that it dries in the desired style? In the latter case, wet hair is more flexible and deformable due to the hydrogen bonding of absorbed water with amino acids in the keratin protein fibers of the hair cortex. These bonds supplant the intermolecular bonds within the keratin itself, giving wet hair a malleability that allows simple styling without the need for styling additives. However, this hold is not very durable, especially in high humidity. The set relaxation time of simple water-styled coiffures depends on the relative humidity of the environment since it re-plasticizes the hair keratin. Hair care researchers have even devised mathematical formulas to define the process of curl set relaxation, which could be used to evaluate ingredients and formulations.1
While water-set, comb-and-go hair styling is enough for some, many consumers want something more substantial. The style they worked hard to achieve should last until they touch-up or restyle hair. This is one performance property required in a styling product. Common hair styling aids to help hold hair in place encompass a wide range of products; from polymer solutions delivered as simple liquid or foamed into mousse, to gels of varying viscosities and film stiffnesses. The essential elements of a natural hair styling liquid or gel are: a film-forming substance to keep hair in place, and a base to deliver it. This base may be as simple as thickened water or as complex as a gel or cream.