Advances in Hair Styling 418 We can now describe each of the major product forms of styling products. Formulation of hair styling gels: An influential factor in the development of hair gels was the introduction of carbomers to the personal care industry by B.F. Goodrich in the late 1950s,1 providing formulators with a whole new avenue of applying fixative resins to hair from product forms other than hair sprays. To this day, carbomers are used as a primary thickening agents for hair gels. It is necessary to capture at least the main features of these polymers that make them so extraordinary as vehicles for the application of styling resins to hair. Carbomers are lightly cross-linked polyacrylic acids. When properly dispersed and neutralized by an alkali or organic amine, they form a thick, clear gel. The gel has the rheological property of being very shear thinning. At rest, the gel is very thick but when sheared, such as by rubbing the gel in the hands, the viscosity goes down precipitously however, once the shear is removed the viscosity goes back immediately to its normal state, a property that is termed pseudoplastic.2,3 This rheological behavior is very important when applying product to hair since the gel has to thin down so that the fixative polymer in the gel can form a uniform thin coat on literally thousands of fibers as it is being worked into the hair. Although gels can be made using polymers derived from polysaccharides, the resultant gels have a mucilaginous texture which retards the proper spreading of the fixative resin through the hair. The result is a gummy feel during application instead of the smooth and penetrating feel of a carbomer gel. However, it is a common practice to blend a carbomer with polysaccharide type polymers, such as hydroxyethylcellulose, to modify feel properties during application. Since the introduction of carbomers, there has been much advancement in the technology, such as improved dispersability, emulsion polymerization, and hydrophobic modification, allowing for more formulation versatility and processability. Ingredients used as fixative resins as well as those that serve auxiliary effects cannot have negative effects on the rheology of