638 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS REFERENCES (1) J. Soc. Cosmetic Chemists 3 216 (1952). (2) W. W. Myddleton J. Soc. Cosmetic Chemists 4 150 (1953). (3) K. R. Dutton and W. B. Reinisch Soap Perfumery • Cosmetics 31 44 {1958). (4) G.E.New J. Soc. Cosmetic Chemists 11 390 (1960). (5) G.E.New in A. W. Middleton, Ed. Cosmetic Science 196oe 257 {1963) (Pergamon Press, London). Introduction by the lecturer The method which we adopted does not do away with the necessity of shampoo evaluation by salon or panel testing. It is possible to detect differences in shampoos using this home assessment technique which it is extremely difficult to confirm in the salon, and I do not think we ought to lose sight of the fact that what cannot be seen in the salon probably cannot be detected by a customer washing his or her own hair. The method proposed needs great attention it is essentially a method of technique and to obtain reasonable reproducibility of results it is essential that all operations must be checked and the techniques involved must be completely reproducible. The time taken for beating up the shampoo is important, and the temperature of the lather produced is also important during the estimation of viscosity. As long as the times and temperatures are strictly adhered to, fairly good reproducibility can be obtained, and we find that these tests are saving us a considerable amount'of time particularly where we are trying to evaluate a considerable number of shampoos we find that this method enables us to decide whether or not any particular formula- tion is worth checking in the salon. The use of a reference standard is of importance, and we selected tri- ethanolamine lauryl sulphate. Each batch of soil appears to have slightly different properties, and it is therefore essential that each new batch pre- pared should be checked against a standard of some kind. DISCUSSION MR. L. DEADMAN: Tests for foam characteristics get more and more complicated, yet some acceptable method of screening shampoos, at least for their major characteristic of lathering, would be of great value in order to check whether they are worth further testing in the salon. Have you tried the very simple method of just using a standard volume of shampoo, say 0.3 ml to wash the hands ? Obviously the lathering property of a shampoo is felt mostly by the hands. In our laboratory we find that the hand washing test gives the best correlation to actual use that we have been able to devise. Many different formulations can be tested in the course of just a few minutes. It is, however, essential, that the hands must be thoroughly

MODERN TRENDS IN THE ASSESSMENT OF SHAMPOOS 639 washed free of grease, etc., before commencing the tests. What are your views on this ? THE LECTURER: We have carried out tests of this type ourselves. The great difficulty on using such tests is that it is possible to modify the structure of the foam depending on the way the hands are rubbed together, and on the amount of air that is squeezed into the lather. I believe that the method of generating the foam is likely to vary over different periods, and it is doubtful whether you could reproduce a standard rubbing technique which is likely to remain standard over the years. This is one of the reasons why we do not use this sort of evaluation method ourselves. I agree that if this test is used, it is essential that the hands should be completely clean before starting, otherwise the first one or two tests will probably give very strange results indeed. DR. A. W. HOLMES: Having been involved in these tests from its initia- tion, I would like to add something to the lecturer's reply. The difference between this test and, for instance, the hand washing test is that quantitative results are obtained. The foam viscosity and the specific volume are known, and this cannot be determined by the hand washing test. If we are going to make any improvement in shampoo quality it will be a gradual improve- ment which will ultimately result in overall benefit. You cannot achieve this gradual improvement by a crude technique such as hand washing. Have you ever tried a shampoo which is a poor emulsifier ? The essence of the test which you are operating at the moment is that the grease is emulsified to some extent during his heating up process, and if this does not occur you may find spurious results. THE LECTURER: We have looked at products which are poor emulsifiers, and it is quite true that one may get results which are misleading by this technique of evaluation. This is one of the reasons why I mentioned that the test is really valuable for screening formulations, and the value of the product as a detergent is assessed in the salon tests. Screening new products or new chemical entities, we would not consider a particular chemical entity to be acceptable as a shampoo on the basis of these tests. We would screen out a lot which we would consider to be unacceptable in a salon, and we would pick up the ones that were poor emulsifiers or detergents in our salon tests.