304 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS package open for any length of time, or on top of a hot radiator, or spill water on it. All of these things may happen to any one and all cosmetics. Some cosmetics can withstand these conditions better than others depending on the sus- ceptibility of the product, different tests have to be designed. In the time allotted it will not be possible to discuss every test in detail. There .will be some tests omitted because they are not made regularly. Furthermore, most of the tests are simple ones but every one of them has been time tested and is run as a matter of routine. We do not claim originality for any of them.. At the outset, a few false ideas should be corrected, such as, that an oven test is necessarily an accel- erated stability test and that keep- ing products in the sample room for weeks and months represents neces- sarily a shelf test. Make-up items are numerous but a discussion of their stability tests can be simplified by considering their physical characteristics rather than their chemical compositions. We have make-up items in loose powder form, dry compressed cakes, all oil preparations, emulsions, and suspensions. Make-up products in emulsion form are, right now, very popular. Loose F^cE PowI)ER A loose face powder is a dry mixture of pigments, inerts, and perfume. The most common rea- son why loose face powder loses its salability is in the loss of perfume. The stability of the perfume in a particular face powder can be readily checked by using the method of minimum quantity to discover whether perfume and powder are not reacting with each other. For this test one uses not more than 1/10 of 1 per cent perfume a good per- fume and suitable powder should maintain a slight but agreeable per- fumed note for at least two days while kept in a vessel open to the air. The usual failure is the dis- appearance of all of the perfume or the appearance of a phenolic or medicated odor. There is a great deal of difference between different perfumes and ingredients in the powder. The stability of the pigment used is of great concern to every manu- facturer of face powder. Unfortu- nately, not all shades can be pro- duced with earth colors exclusively and we are forced to use some or- ganic lakes and toners. These should be used very sparingly because they are not light-stable for any length of time. A simple stability test to check the light stability is to place a small puff on the smoothened surface of loose face powder and then put the sample into bright sunlight for about thirty minutes. Any appreciable bleaching action of the unprotected area will indicate possible trouble. Ordinarily, the other white ma- terials have less influence on the stability of the face powder. One exception may be zinc stearate. Zinc stearate has a tendency to de-

STABILITY TESTS ON MAKE-UP ITEMS 305 velop an oder on aging. However, a good grade of zinc stearate should allow the rubbing into slightly per- spiring skin without developing a rancid or off-odor. Certainly, just smelling the dry zinc stearate will not give an indication of its keeping qualities. COMPACTED MAKE-UP ITEMS In recent years a number of cos- metics have been merchandized in cake or stick form. Of course, dry rouge has been with us for many years, but cake make-up and cron- pact powders are of more recent ori- gin. In these products breakage is probably the most important factor for rejection. To test the strength of compact powder, we use penetrometer and drop tests. The penetrometer needle drops from a height of 1 cm. onto the cake and its penetration is a measure of hard- ness. A cake of compressed powder has to withstand more than 10 drops from a height of 1 foot on a thin metal plate cushioned by a few sheets of paper. Some compacted powders have excellent cosmetic properties but are very fragile. Here we have developed a package tumbler which allows us to test the best way of packaging a more fragile product. The latter test is complemented by actual test shipment across the con- tinent and back. Face powders, either loose or compressed, are used with puffs many of the puffs are glued with latex, containing paper as a cush- ion, and for this reason the influence of ammonia and sulfur dioxide has to be considered. LIPSTICK The most important of all make- up items is probably lipstick. There are quite a few things and conditions which can make a lipstick unsalable. To name a few:breakage under use, excessive sweating, rancidity, loss of perfume, uneven shading, no staining, loss of stain, melting in the show case, attack of the case, or discoloration of the case on the lipstick. Every time a new reason or new conditions are found which are objectionable to the ulti- mate consumer, a test is set up to anticipate the encountered condi- tions and catch it before it leaves the factory. With this in mind, we have tests for melting points because we know that if the melt- ing point of a lipstick drops below 60øC., we will certainly have a number of complaints of melted and deformed lipsticks. Anybody who has given any thought to es- tablishing a melting point procedure for lipsticks has developed an in- feriority complex because, frankly, a lipstick mass does not have a melting point, for in the final analy- sis, all lipstick melting points are viscosity or plasticity measurements. Plastic flow is a question of tem- perature and pressure. When this is realized then the strictest ad- herence to prescribed testing con- ditions becomes most important. Usually each laboratory has its own "melting point" procedure and results are not interchangeable.