JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS for an hour. The foam with no lauryl alcohol also collapsed soon after discharge, but the remainder of the foams retained their shapes for at least an hour. However, those that wet paper became quite thin on aging as a result of loss of liquid from drainage. In this series, as in many of the series to be discussed later, it is possible to select foams which wet and collapse, or which wet and retain their structure, or are quite stable. Variation in t•ropellants The effect of different propellants upon the properties of sodium lauryl sulfate/lauryl alcohol systems is shown in Table III. Freon-12 and Freon-12/Freon-114 (40/60) gave foams with the lowest drainage rates, and Propellant 152a and Propellant 142b gave foams with the highest. The former two propellants gave the stiffest foams and the latter two the lowest density foams. Wettability data generally correlated with the foam drainage results. The foams with Propellant 152a and Propellant 142b wet paper within five minutes after discharge. The foams with the other propellants did not wet during at least one hour after discharge. The foam with Pro- pellant 152a collapsed within 15 minutes and that with Propellant 142b collapsed within one hour. The other foams retained their shape. Microscopic examination did not reveal any significant differences between foams formulated with Freon-12, Freon-12/Freon-114 (40/60), Freon-114, or Freon-12/Freon-ll (50/50). However, the foams with Propellant 142b or Propellant 152a had much larger laminae that Table III Variation in Propellant--Sodium Lauryl Sulfate•/Lauryl Alcohol Systems b Foam Properties Emulsion Properties Drainage Stiffness Density Type of Propellant Viscosity Stability (2 hr) (g) (g/co) Discharge Freon-12 High 5 hr 20 28 0. 061 Slightly noisy Freon-12/Freon-114 (40/60) High 5 hr 0 44 0. 062 Quiet Freon-114 High 5 hr 0 48 0. 073 Quiet Freon- 12/Freon- 11 (50/50) High 5 hr 2 16 0. 059 Noisy Propellant 142b High 5 hr 41 16 0. 043 Slightly noisy Propellant 152a Medium 5 hr 84 14 0.039 Slightly noisy Sodium lauryl sulfate concentration = 0.10 M. Sulfate/alcohol ratio (molar) = 1:1.

Figure 4. Photomicrograph of a sodium lauryl sulfate/lauryl alcohol foam with Freon- 12/Freon-114 (40/60) propellant .., :.... Figure 5. Photomicrograph of a sodium lauryl sulfate/lauryl alcohol foam with fiuorocarbcm 142b as the propellant