The washing process whereby soils are removed consists basically of applying mechanical action to loosen the dirt particles and dried matter in the presence of water which helps to float off the debris and acts, to some extent, as a dissolving and solvating agent. Greasy soils are hardly removed by washing in plain water; and natural waters, in addition, often contain impurities such as calcium salts which can react with soils to make them more difficult to remove. Therefore, detergents are used. The detergent active is that substance which primarily acts to remove greasy soils. The other constituents in a built detergent assist in this and in the removal of dirty stains and the hydrophilic sticky or dried soils.

As is well known, detergent actives belong to the chemical class consisting of moderately high molecular weight and highly polar molecules which exhibit the property of forming micelles in solution. Physicochemical investigations of anionic surfactants, including the soaps, have shown that there is little polymerization or agglomeration of the chain anions below a certain region of concentration called the critical micelle concentration. (1) Below the critical micelle concentration, monomers and some dimers are present. (2) In the critical micelle region, there is a rapid agglomeration or polymerization to give the micelles, which have a degree of polymerization averaging around 60 -- 80. (3) For anionics, these micelles appear to be roughly spherical assemblages in which the hydrocarbon tails come together so that the polar groups (the ionized ends) face outward towards the aqueous continuous phase. Obviously hydrophobic (oleophilic) substances such as greases, oils, or particles having a greasy or oily surface are more at home in the center of a micelle than in the aqueous phase. Micelles can imbibe and hold a considerable amount of oleophilic substances so that the micelle volume may be increased as much as approximately two-fold. Although the matter has not been unequivocally demonstrated, the available data show that micelles in themselves do not contribute significantly to the detergency process.