OPERATING A COSMETIC CLINIC 75 side, of course, was obviously more lustrous. In planning tests, whenever prac- ticable, we arrange for some kind of control. It sharpens observation and brings out points that might otherwise be missed. In many cases--nail polish, for example--the control may be a similar cosmetic with which we are thoroughly familiar. In checking a hand cream, we may use an untreated hand as a control for a treated one. In the case of an emollient face cream• we may take careful ob- servations of the skins of a group of testers, and after two weeks' daily use of the cream, examine the skins again. To make certain that judg- ment is accurate and unbiased, the final examination is often made by two persons--the one who super- vised the study, and some one who has not seen the notes taken of the skin condition before the cream was applied. This examination by a neutral party helps us to resolve some difl•- cult questions. Some time ago, the laboratory, in reporting on a cream shampoo, commented that the label included the claim, "Contains lano- lin." The amount it contained was very small. We were doubtful that such a small amount of lanelin was significant enough to warrant its mention as an active ingredient on the label. We decided the point by practical test. The manufacturer made up some of the product with- out lanolin. We shampooed six subjects, using the shampoo with- out lanolin on one side and with lanolin on the'other. Then a woman who did not' know what had been done was asked to tell which side of the hair was softer and smoother. She ran her hands over each head, and, to our surprise, in all six cases picked out the side washed with the product containing lanolin. In another instance, we wanted to know whether a hand lotion used before washing dishes really pro- tected the hands and helped to keep them soft. We co-ordinated our study with a dishwashing study the Institute was making, in which a number of girls washed specially soiled dishes twice a day for five days. Before each one tackled the dishes, we rubbed one hand with lotion, taking care always to treat the same hand. At the end of the test, two men--engineers in the Institute--were asked to tell which hands were softer. As you might expect, these men made interested and excellent judges. Their ob- servations agreed with those of the test supervisor, and we had elimi- nated any possibility of bias, again proving the usefulness of a neutral party. A question that arises immedi- ately in planning a test is, "How many subjects do we need?" That depends entirely on the type of product and what we are trying to find out. If the product is new, as cake make-up was a few years ago, more testers are necessary than if the product is a familiar one. If the ingredients are now and un- tried, as soapless shampoos were some years ago, many more testers

76 JOURNAL OF THE SOCIETY and much more time is called for. A good deal depends' on whether clear-cut evidence can be expected, or whether it is likely to be conflict- ing. Trying out a bubble bath is a simple matter. The consumer ex- pects it to have a pleasant smell, to make plenty of bubbles that last long enough for her to relax and enjoy them, and to leave no ring on the tub. We can judge the quantity and lasting quality of the bubbles very quickly in a laundry tull, a half a dozen women will give us a good idea of how satisfactory the product will be under varying con- ditions in the home. But if you want to know whether a face powder cakes and how well it clings, you may need 20 or more subjects because you are bound to have some contradictory results. In general, when we have a com- plicated problem, I have found that it is better to begin with a very small number of subjects, and enlarge the study after we have had some ex- perience with a product. The time required for an adequate use ,test is sometimes surprising to those who are not accustomed to this method of investigation. It may vary from a few days to a year or more. Consider, for example, a product with this claim, "Eliminates broken, brittle nails helps nails grow long and strong." This prob- lem was brought to us last spring. The plan for our test required 20 women to .come to the Beauty Clinic twice a day to have their nails treated. Since we have a OF COSMETIC CHEMISTS five-day week, they were given a supply of the product to use them- selves on Saturday and Sunday. To determine- how long the study should continue, we figured that it would take two months for the old nail to grow out completely and two months more for a new nail to grow out to the tip. So the mini- mum time was set at four months. I am sorry to report that at the end of this tedious study, we saw no difference in the quality of the nails. As I have explained, most of our practical use tests are supervised in the Beauty Clinic. Sometimes, however, we find it advisable to have groups of women make home tests. For example, in studying a plastic cuticle pusher, we thought the tip might be too sharp and in- jure the cuticle when used by un- skilled hands. A group of 20 women who used the pusher for a month de- cided this question for us. We also like to have large groups o5 home testers use products to determine whether directions for using are clear and adequate, or to learn whether they will follow directions contrary to their usual habits. These practical use tests have been of enormous value to us when we want to know whether a cos- metic works'and will satisfy the average user. They have enabled us to recommend confidently a large group of excellent cosmetics. At the same time, guided by them, we have rejected such disappointing items as a bubble bath that doesn't bubble, a cake make-up so hard it won't come off the cake, or one that