228 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lather drainage time measurements (Figure 3) and was readily apparent during the test. Na laureth(3)sulfate-lauramide DEA mixtures, for instance, formed freeflowing, "soupy" lathers which lacked strength and integrity. Clearly, if one assumes that the use of an additive which yields a prolonged Ross-Miles foam-decay time would also lead to the enrichment of lather, there would be the possibility of being misled. The Ross-Miles test is usually run at a low active concentration (ca. 0.1%) which, under the rather static conditions of the test, yields a loosely structured foam. Additives, such as lauramide DEA, which prolong the decay rate of simple foams are useful in bubble bath and hand dishwashing products. Under higher active concentrations and more dynamic conditions, however, they seem to have an adverse effect on lather quality. The relatively poor lathers obtained with Na laureth(3)sulfate, even under the rigorous conditions of the test, prompted us to examine the effect of the addition of sodium lauroyl sarcosinate. As the curves in Figure 4 indicate, this addition of sarcosinate substantially improved the lather drainage times. Lather drainage times versus concentration for other commonly used surface active materials and selected mixtures are presented in Figures 5 and 6. LATHER OF SURFACTANT MIXTURE RATIOS AT A FIXED ACTIVE CONCENTRATION Since modern shampoo formulations are composed of two or more principal surfactants and lather boosters, it is natural to examine mixtures of this type in order to determine interactions and find a ratio which produces best results. In attempting this, we have fixed the total surfactant concentration at 1% active as this concentration is drain time, sec. 80 2:1 Na Laureth (3) Sulfate: Na Lauroyl Sarcosinate Na Laureth (3) Sulfate I 60 40 20 0 0.3% 0.6% 0.9% Surfactant Concentration Figure 4. Lather drainage time versus concentration. 1.2% active

LATHERING POTENTIAL OF SURFACTANTS 229 80 2:1 Amphoteric 2: Na Lauroyl ----,.• Sarcosinate/ drain time, 20 0.3% 0.6% 0.9% Surfactant Concentration Figure 5. Lather drainage time versus concentration. 1.2o/o active 80 drain time, • •NA•oxø inUc•.4 Sulfate Disodium MIPA-Sulfosuccinat• 60 40 20 0 0 0.3% 0.6% 0.9% Surfactant Concentration Figure 6. Lather drainage time versus concentration. 1.2% active