HAIR ROUGHNESS AND SOFTNESS 255 150 95% confidence limit 140 130 o• 120 • 110 STANDARD ...... 100 .................... 6'i/qõ• .... 80 • A-1 A-2 A-3 B-1 B-2 B-3 SAMPLE {shampoo) Figure 3. Effect of experimental shampoo treatments on frictional drag (wet condition). scores obtained by expert panels in Figure 5, a very good correlation was obtained also for these commercial shampoos. The composition of the shampoo showing the worst score (most roughness) consisted of cocamide DEA and laureth sulfate detergents, with no conditioning agent. The compo- sition that provided the best smoothness effect consisted of cocamide DEA, lauryl be- taine, and methyl cocoyl taurate detergents, with the highest level of polyquaternium- 10 conditioning agent. Measurement in air flow. In the case of the measurement of air flow (the measurement of interfiber friction of dry hairs), the humidity is expected to be influential. Therefore, the relative humidity (RH) was varied to 30, 50, and 70%, and the frictional drag, F value, was measured for the hair strands treated with the standard shampoo and those treated with the standard rinse. The flow rate of air was from 18,000 to 20,000 ml/ Table II Roughness Evaluated by Expert Panels (Experimental Shampoos) Friction Large Small (roughness) (sleek) A-1 B-1 • A-2 A-3 B-2 B-3 Evaluation A-1 A-2 -- A-3 by expertpanels B-1 B-2 B-3 Polyquaternium- 10 0.2% 0.5 % 0.8% Evaluation by expert panels A group B group Cocoamphoglycinate 0% 2.4%

256 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 110 100 ............... A B C D E SAMPLE (rinse) 90 8O '7O 50 950//0 confidence limit STANDARD RINSE Eva luat ion by expert panels ABCD=E Figure 4. Effect of experimental rinse treatments on frictional drag (wet condition). min. The FDR values expressed as the percentage of the FDR value for the hair strands treated with the standard shampoo under 50% RH are shown in Figure 6. Under all humidity conditions tested, rinsed samples showed smaller FDR values than shampooed samples, reflecting the smoothing effect of hair rinses. As the relative humidity was 150- 140 - 130 - 120- 110- Commercial shampoos 95% confidence limit _• STANDARD lOO .................... ........................................ ......... 90- I 2 3 4 5 6 sleek roughness Evaluation by expert panels Figure 5. Relation between FDR and evaluation by expert panels on commercial shampoos.