488 JOURNAL OF THE SOCIETY OF COSMETIC, CHEMISTS • 50 .c 40 ._E 20. .m_ C2 10 # d 0 101 10 2 10 3 1'04 cps Viscosity ,4p = 90 % Zip = 8O % Figure 5. Discrimination threshold for viscousness of cream base substances in relation to viscosity t- 'i, 50 ,40 30 20 10 ....... ZIp = 90% --,4p = 80% 0 10 • 10 2 lb 3 10 4 g/cftC Hardness Figure 6. Discrimination threshold for firmness of mechanical spring in relation to hard- ness

SENSORY FIRMNESS AND VISCOUSNESS 489 Sample Group Table IV Discrimination Thresholds of Firmness and Viscousness of 80% and 90% Correct Judgements (Standard Substances) Firmness (Spring) Viscousness (Silicone Oil) Average Discrimination Average Discrimination Hardness Threshold Sample Viscosity Threshold (g/cm 2) (%) Group (cps) (%) P=80% P=90% P•80% P:90% F G H I 2.54 x 108 8.0 11.5 J 1.49 x 10 * 15.5 27.5 8.47 x 10"9.5 16.0 K 6.43 x 10 •' 16.5 27.0 2.77 x 10" 6.0 10.0 L 1.98 x 10 • 12.5 17.5 1.06 x 10 -0 9.0 17.0 M 3.19 x 10222.5 37.5 N 1.72 x 10-0 30.0 47.5 o 50 ...c 40 o 30 '½- 20 • •0 k K 0 10 4 10 2 10 3 10 4 cps Viscosity ....... /Ip = 90 % • ,,lp = 80 % Figure 7. Discrimination threshold for viscousness of silicone oil in relation to viscosity members were able to discriminate the samples if the relative difference of sample's hardness was about 10%. In the ease of viscousness, as is shown in Fig. 5, there was the tendency of becoming easy to discriminate as the viscosity decreased however, the ex- treme decrease of viscosity, as in sample e, showed a reverse effect. Sample group d showed the easiest discrimination. Based upon these results, it was found that the discrimination threshold of sensory firmness and viscousness changed continuously depending upon the changes of the instrumentally measured hardness and viscosity of the