320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS coil coming out of the bath has a needle valve attachment so that the flow of propellant out of the cylinder through the cooling coils may be controlled. When the can and contents have been cooled to below 0øF the propellant is added until the desired weight is obtained. In this manner the propellants may be handled with a minimum loss. The can is then seamed and placed in hot water bath to be tested. Visual observations are made weekly on the pressure flasks to determine how the component parts are holding up. Any adverse action can be readily determined and noted. In the regular cans corro- sion is usually determined by spray- ing and noting the change in odor or pressure. These cans are also cooled in the deepfreeze and opened te determine the extent cf the damage of the can and valve parts or any change that may have taken place in the contents. In the case of corrosion or decomposition there is usually a change in color of the contenl•'s or a definite mal odor of the contents coupled with very serious attack on the can parts or the valve parts. The 130 ø test, like any other accelerated test, is not completely reliable. Before a final decision is made, therefore, the results at room temperature must be taken into consideration. Where the 130 ø test has been satisfactory the room temperature tests have also been satisfactory. In some cases where the 130 ø test has been unsatis- factory after a period of one month, we have found that room tempera- ture samples for a period of one year have been completely satis- factory. In these cases an 18- month test at 100øF must be satisfactory unless formula revision can be made. It is also true that actual produc- tion conditions cannot be fulfilled in the laboratory. It is therefore a nec- essary part of stability testing to make a production run of between 1000 and 5000 cans on the pro- duction line before a product can be given a go signal for the market. The problem of perfuming pres- sure products is particularly im- portant. It has been found that perfume compounds will stand up well in the concentrate in contact with glass but will show marked evidence of decomposition and sub- sequent odor change when used in the container. Many of the per- fume compounds themselves are a cause of corrosion. A great deal of work has been done on this problem by the essential oil suppliers and pre-tested materials are now available. However, it is abso- lutely necessary to test every per- fume compound under the exact conditions that it is to be used. To complete the picture for a successful product the evaluation of stability tests is not final. It is necessary that the concentrate formulas be controlled very accu- rately for quality and composition. In waterless products it is specially important to check moisture con- tent, free-acidity and specific grav- ity. In water base products, pH and specific gravity play an impor-

THE SKIN TESTING OF NEW COSMETICS 321 tant part. Rigid specifications should be set up and quality control maintained on container and valve material. Stability testing of aerosols al- though perhaps a little more compli- cated and painstaking than the stability testing of other cosmetic preparations is still a matter of being practical. From the above discussion you might probably say to yourself, "It takes a long time, we cannot wait." My sincere answer to that attitude is that an aerosol product cannot be placed on the market under any other conditions. There is no compromise for running the stability and control tests on low- pressure aerosols. THE SKIN TESTING OF NEW COSMETICS* By Louts SCIW^P. TZ, M.D. trashington 6, D.C. THE CLOSED patch test was devised many years ago by Jadas- sohn as a means of finding the irri- tant in cases of contact dermatitis. It is a diagnostic procedure. The skin testing of new cosmetics is comparatively recent and is still in the stage of development. The prophetic patch test was devised about 14 years ago while I was in the U.S. Public Health Service to test the possible irritant properties of the then new synthetic fiber now known as nylon. It came about as follows: before nylon was placed on the market, the manufacturers asked the U.S. Public Health Service to devise a test which may show whether gar- ments made of the new synthetic fabric would be safe to wear. The result of this request was the pro- phetic patch test. * Presented at the May 18, 1951, Meeting, New York City. The original prophetic patch test consisted in placing a half-inch square piece ofunprocessed nylon on the skin of 200 subjects, covering it with a piece of cellophane 1 inch square and sealing this on the skin with a piece of adhesive plaster 3 inches square. A piece of un- bleached unprocessed cotton fabric of similar size was fastened on the skin of the opposite side of the body to act as a control. The patches remained on for forty-eight hours, then removed and the reactions read and recorded. The sites of the patches were ex- amined for 3 consecutive days for late reactions. Ten days after the last reading the patch testing was repeated on the same 200 subjects and on approximately the same skin areas. The patches were removed after forty-eight hours and the sites examined for signs of reactions for three consecutive days. The second