MEASUREMENT OF STATIC CHARGE ON HAIR 471 by use of the Polaroid camera with proper control of the speed of combing and rate of sweep across the instrument it is possible to obtain a time ex- posure photograph showing the results of three or four successive comb- ings. Such a photograph is shown in Fig. 3a for the results of an experiment on combing a hair tress following a conventional shampoo treatment. The relatively high static charge obtained is evidenced by the height of the peaks above the base line. In Fig. 3b there is given for comparison the results obtained when the shampoo is followed by a cationic creme rinse treatment. The low peaks obtained after creme rinse as compared to the higher ones from the shampoo alone are an indication of the much .{• ?.'" •'•".' .• 5'..:.•=.::.•5•'• :-. ...... =e r •q'7'- . ß •..• ....... . .'.. Figure 4.•Procedure used for measu•ment and •cording of cha•e generated in combing of model's hair. smaller static charge developed. This difference in static charge accords well with the known antistatic properties of the cationics. Good correlation has been observed between the height of the pip and the extent of ballooning in the previously described procedure. (c) To carry the application of the oscillograph into even more realistic testing, work was undertaken to use the oscillograph method just described on models' heads by use of half-head techniques in which an experimental product was used on one side of the model's head and a control product on the other side. The procedure for determining static charge was identical with that already described except for the necessary modifications for dealing with live subjects. Tests were run in an air conditioned labora-

472 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE I--PER CENT REDUCTION IN STATIC CHARGE USING CREME RINSE Y oR Z FOLLOWING SHAMPOOS A, B, C, D, E, F, G oR H (HA•.F-HEAD TECHNIQUE ON MODEkS) Creme Creme Creme Creme Rinse Rinse Rinse Rinse Y Z Y Z Shampoo A 91, 75 63, 59 Shampoo D 83, 75 72, 78 87, 90 67, 84 Shampoo E 85, 74 85, 46 87, 89 71, 66 Shampoo F 85, 79 80, 73 Shampoo B 84, 81 27, 72 Shampoo G 79, 64 75, 75 Shampoo C 67, 56 64, 44 Shampoo H 49, 95 46, 79 tory but necessarily without the precise control on humidity which we maintained on the tress work. Readings were taken within a few min- utes after use of the hair dryer, merely permitting the hair to cool slightly before running the combing experiments. In Fig. 4 there is shown the entire operation of combing and photographing the results. One operator does the actual combing while the other takes the picture. A study was made of the relative charge production, using half-head technique, of a number of leading shampoos as compared to the same shampoos followed by cationic rinse. Several different rinses were tried in these experiments. As will be seen in Table 1, in every case a substan- tial reduction was obtained on use of the cationic rinse. Per cent reduc- tion was calculated from the differences of the summation of the peak values between the shampoo and shampoo plus rinse divided by the summation of the peak values for the shampoo. From the data in this table an idea may also be obtained of the reproducibility of these effects as measured by the oscilloscope. This technique was also employed to determine the duration of creme rinse effect under actual usage conditions. Subjects were given a con- ventional whole head shampoo and oscillograph readings taken daily for TABLE 2--OscILLOGRAPH READINGS SHOWING DURATION OF CREME RINSE EFFECTS ON MODELS , -Averages of Peaks. , After Treat- 2nd 3rd 4th 5th 8th ment day Day Day Day Day Model I Shampoo 11.2 7.9 11.0 10.2 8.9 9.6 Shampoo d- Rinse 1.1 1.1 2.2 1.8 2.9 7.5 Model II Shampoo 14.0 11.0 13.2 13 4 11.0 6.4 Shampoo d- Rinse 2.5 1.9 3.4 3.4 3.2 7.6 Model III Shampoo 16.1 13.5 14.5 12.8 12.9 11.0 Shampoo d- Rinse 1.8 3.4 5.4 6.1 8.7 8.5 Model IV Shampoo 12.2 12.2 10.2 14.6 9.7 9.9 Shampoo d- Rinse 2.3 1.8 4.3 4.3 10. $ 6.0