330 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The above method is a widely accepted method. We would at this time like to present another method which is to be used as a supplementary method for the patch test method and which, we might say, our experience has shown to be a more accurate method for deter- mining sensitizing materials. The method is one developed by Dr. John H. Draize, of the Division of Pharmacology of the Food and Drug Administration and the author. It was during a discussion with Dr. A. J. Lehman, Chief of the Division of Pharmacology, of the Food and Drug Administration and his group, that Dr. Draize's method was pre- sented to us as a suggested method on human subjects. The method which has been called the "repeated insult method" is as follows: The material to be studied is placed in contact with the skin of the subject. It is kept in contact with the skin for a period of four to twenty-four hours every other day until ten such applications have been made. At the end of this period there is permitted to elapse a space of three weeks, then the sub- stance is again placed in contact with the skin for a period of twenty- four to forty-eight hours. We have been able to pick up sensitizing substances much more rapidly with this method than we have with a second application on the patch test method. But since this method is fairly involved, it is suggested that it be used on as large a number of subjects as possible and if possible 200 subjects but, where this is im- possible, to get this information on at least a group of 25 to $0 subjects. We feel this method is capable of de- tecting sensitizing substances which have a lower threshold of sensi- tivity than that which might be detected by the other patch test method. We are often asked to study a material and compare it with a second material designed for similar use. We are often asked which is less irritating? Is "ours" less irri- tating? This can be determined by running a series of concentrations of both substances and determining at which concentration the irrita- tion appears. If one material ir- ritates at higher concentration than another material it may be said to be less irritating than the material that irritates at a lower concentration. This data, while it may be factual, does not necessarily mean anything in practice since it is quite possible that the substances will never be used in the concentrations which were tested. In other words, in the "inuse" concentrations, neither one of the substances may be irritating. In conclusion, I wish to point out that the human skin test method of Schwartz may be regarded as a basic technique which must be used intelligently, with several things in mind. Length of time of contact, concentration of material, and use of material and body surface cover- age are the most important factors concerning the modification of the test method. The method of de- termining sensitization as suggested by Dr. Draize is an important con-

EVALUATION AND TESTING OF NAIL LACQUERS 33I tribution to the human skin test is as conclusive as the actual use method. Finally, it must be re- of a material by large numbers of membered that no testing method people. EVALUATION AND TESTING OF NAIL LACQUERS* HENP, Y J. WING, PH.D. Northam l/Farren Corp., Stamford, Conn. As You ALL know, nail pol- ishes are nitrocellulose lacquers. The testing of nail polishes may be covered quite simply by stating that these lacquers should be sub- jected to the same tests as those applied to any lacquer of this type. However, this leaves the newcomer in this field quite at loss for the usual tests for lacquer are probably unknown. Before proper testing can be done on any product it is necessary to first determine the characteristics of a material which gives customer satisfaction. In a nail polish, color is probably one of the most im- portant properties. We also find that ease of application, rate of drying, wear resistance are all part of the customer reaction to any polish. Fortunately the chemist does not choose the color which is to be sold. This selection. is usually made by the-promotion department. The formulator simply makes up colors which he hopes will meet the re- quirements of those who make the * Presented at the May 18, 1951, Meeting, New York City. final selection. However, once this selection is made it is then the job of the production and control de- partments to see that every batch of this shade matches the standard selected. This standard needs to be estab- lished first. It is often done by using pour cards made by pouring a coating of the colored lacquer on white Bristol board followed, after drying, by another coat which leaves some of the first coat un- covered. This standard is pre- pared from a laboratory sample of the polish which has been approved for color. Experience has shown that the dry pour cards kept away from the light when not in use undergo practically no color change. However a liquid sample of the same polish will change color quite rapidly and will lose its value as a standard. Having established the standard it is necessary to compare the batch with this. Another pour card on similar stock is prepared using liquid from the batch. After drying this is compared with the original standard pour card and of