CLEANING HAIR 311 Table I Artificial (Spangler) Sebum (8) Ingredient % Linoleic acid 5.0 Squalene 5.0 Oleic acid 10.0 Coconut oil 15.0 Olive oil 20.0 Cholesterol 5.0 Stearic acid 5.0 Palmitic acid 10.0 Paraffin 10.0 Spermaceti wax 15.0 HAIR SUBSTRATE In all experiments, dark brown, Oriental hair, virgin quality and of 10-inch length was used (DeMeo Brothers, New York). Prior to soiling with sebum, the hair was divided into approximately 3.5-g tresses, washed with 10% TEALS (Standapol T, Henkel) for one minute, rinsed for two minutes under running tap water (105øF), and air dried at room temperature. Tresses were conditioned in a humidity room, 70øF and 60% rela- tive humidity, for 72 hours prior to soiling with sebum. All subsequent weights of hair were made after similar temperature and humidity conditioning. SURFACTANTS SLES-2 and ALS were obtained from Henkel Corporation (Standapol ES-2 and Stan- dapol A, respectively), and SODS-! was obtained from VISTA Chemical Company (Alfonic 8,10-20 ether sulfate). The surfactants were used as provided by the manufac- turer, with no further purification. Solutions were prepared with deionized water. HAIR-SOILING PROCEDURE Hair tresses were soiled by suspending a preweighed tress in a solution of sebum in hexane (3.5 g hair/250 ml solution), at the required concentration. After 20 minutes in the sebum solution (with constant stirring), the hair was removed and the solvent allowed to evaporate from the tress at room temperature. After conditioning at 60% relative humidity, the tress was weighed to determine the sebum load. Soiling solutions of 6 and 3 weight percent sebum were used. A 6% solution was used for soiling tresses subsequently washed with 0.01% surfactant (soil/wash condition A) one-cycle experiment. The 3% concentration was used for soiling 1.8-g tresses of the ten-cycle experiment and for soiling tresses washed with 0.1% surfactant (soil/wash condition B). These sebum concentrations produce soiling levels on the tresses of ap- proximately 0.04-0.055 g soil/g hair and 0.03 g soil/g hair, respectively. Hair soiled with the 3% solution is perceived to be "dirty" or "oily" (corresponding to that on heads of consumers who shampoo frequently), whilst tresses soiled in a 6% solution are "very oily," representing perhaps an extreme in hair oiliness for most Western cultures.
312 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The higher soiling level, however, was most often used in this work as it facilitates the subsequent gc analysis of the sebum. After the soiled tresses were dry, each was split into two swatches of about 1.7 to 1.8 g each. One of each pair was washed with the appropriate surfactant. The other portion remained unwashed and acted as an internal control. This was necessary to compensate for sample-to-sample variation in soiling levels. TEN-CYCLE SOIL/WASH EXPERIMENT For the ten-cycle soil/wash experiment, the tresses were split as described above, with one swatch kept as control. The other portion was then washed and dried (described below) and placed in a constant humidity room overnight. The next day these tresses were soiled again with sebum, allowed to dry at room temperature, and placed in the constant humidity room overnight. The following day the tresses were again washed with the appropriate surfactant. This soil/wash cycle was carried out ten times. The order for both soiling and washing procedures was randomized. HAIR-CLEANING PROCEDURE Cleaning of the soiled tresses was achieved using a bulk process similar to that described in reference 7. The soiled hair tress was suspended in 100 ml of either 0.1% or 0.01% aqueous surfactant at 110øF and agitated (magnetic stirrer) for five minutes. Tresses were then rinsed under running tap water (105øF) for 20 seconds (total rinse volume 500-600 ml). Heat from a hand-held drier was applied for one minute and the drying completed at room temperature. Conditioning in the humidity room followed. These surfactant concentrations are very low and for SODS-1 are below the cmc. Since oily soil removal occurs through solubilization via micelies, we would expect poor re- suits with this surfactant. In fact, even at concentrations above the cmc, SODS-1 is a poor detergent for removing oily soil. It is included in this study as a negative control. EXTRACTION OF SEBUM FROM HAIR Before the sebum residues were extracted, all tresses were placed in a forced air draft oven at 55-60øC for four hours. This helped to ensure a uniform moisture content throughout the sample set. About 1 g of hair from each tress was weighed into a vial, 20 ml of hexane added, and the sealed vial shaken on a mechanical shaker for 30 minutes. Hexane was used as the extraction solvent based on data presented in reference 7. These data claim chromatographic profiles of the hexane extract of sebum-soiled tresses to be comparable to profiles of standard sebum/hexane solutions. After shaking, 15 ml of solution was pipetted from each vial into a previously weighed second vial. The sample was evaporated to dryness (at room temperature) by gently blowing filtered nitrogen over the liquid surface. Subsequently the vials were weighed to estimate total extracted sebum, and the residues analyzed by gas chromatography to determine sebum composition. Sample residues were dissolved in hexane containing internal standard, Eicosane, to a concentration of approximately 6 mg/ml. Sample in- jection amount was 0.4 microliters. The analyses were performed on a Carlo Erba Mega 5360 High Resolution Capillary Gas Chromatograph fitted with a cold on-column
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