Critical Micelle Concentration
Under Construction by Rebecca Perry
The Critical Micelle Concentration (CMC) is the concentration of surfactants in a solution above which micelles form out of any additional surfactant added to the system. Below the CMC, surfactants adsorb to an interface, lowering the interfacial tension, or disperse within the bulk. There may be an occasional micelle formed below the CMC. Likewise, above the CMC, a very limited amount of added surfactants may enter the dispersed phase or adsorb onto an interface. However, above the CMC, the vast majority of added surfactant will form micelles.
The Critical Micelle Concentration is related to the law of mass action. In chemistry, we look at the law of mass action to see how much of a reactant (individual surfactants) will form a product (micelles). Below the CMC, almost no micelles form, while above it, lots of micelles form
The University of Wisconsin, Madison website has a experiment with movies of the steps exploring critical micelle concentration.
 R. Jones, "Soft Condensed Matter," Oxford University Press Inc., New York (2002).
 T. Witten, "Structured Fluids: Polymers, Colloids, Surfactants," Oxford University Press Inc., New York (2004).