78O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Sample Preparation--The shampoo was diluted to the desired con- centration (w/w) with deionized water. If necessary, it was warmed slightly to attain clarity. Gentle agitation followed until the solution was uniform. For "hard water" tests, dilution was only to 98 parts to allow for the addition of Ca + + solution. Procedure--The temperature of the sample was adjusted. For ele- vated temperature tests, the mixer bowl, beaters, and sebum solution were warmed. A 50-g (49-g for "hard water") aliquot was placed in the bowl and the Ca ++ or sebum solutions were piperred in, if required. The beaters were positioned above the surface of the liquid and the motor was turned on. When the speed had equilibrated at 720 rpm, the beaters were lowered into the bowl and timing was begun. After exactly three minutes, the motor was turned off. Specific Foam Volume Equipment--Crystallizing dishes, 50 mm in diameter and 35 mm high of known weight and volume spatula with stainless steel blade. Procedure -Immediately at the conclusion of the beating time, por- tions of the foam were transferred to each of two crystallizing dishes, with care to prevent the inclusion of large air pockets (Fig. 1). The edge of the spatula was scraped across the surface to level the foam. The dishes were weighed to +0.01 g and the weight of the foam was determined. The heavier weight was used in the calculation. Calculation--Volume of container/weight of foam = specific foam volume expressed as ml/g. Reproducibility--Although reproducibility varied with the different test conditions and sample composition, the maximum standard devia- tion was 0.3. Foam Drainage Equipment Stemless funnel, 75 mm i.d., of known volume, fitted at the base with a conical double-thickness l•lug of 20 mesh screen, approxi- mately 20 mm X 10 mm X 15 mm 25-ml tall-form graduated cylinder spatula with stainless steel blade. Procedure -Immediately at the conclusion of the beating time, a por- tion of the foam was transferred to the funnel, with care to prevent the inclusion of large air pockets. The edge of the spatula was scraped across the surface to level the foam. The funnel was positioned above the cylinder and timing was started. The volume of liquid in the cyl- inder after five minutes was recorded (Fig. 2).

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