2 MEASUREMENT OF CRITICAL MICELLE CONCENTRATION

Surfactants are at their most effective at or above their critical micelle concentration (CMC). As the micelles solubilize the soil, the concentration of available micelles is reduced and the surfactant becomes less effective. Therefore, it was decided that the surfactant solutions should be used in concentrations that were several times their CMC. This technique allows for some of the surfactant micelles to be used up during the washing process without reducing the cleaning efficiency. In textile conservation, surfactants are used at 2 to 10 times the CMC, with the higher values saved for heavily soiled textiles. For the purpose of this experiment, the surfactants were tested in a solution at five times their CMC. Most of the manufacturers were unable to supply CMC values, and so the CMC had to be determined experimentally. The technique used for the determination of the CMC was Sugden's bubble method (Sugden 1922, 1924).