COLOR MATCHING IN THE COSMETIC INDUSTRY* By E. I. ST• ^RNS Research Department, Calco Chemical Division, •tmerican Cyanamid Company, Bound Brook, N. •. THREE physical factors enter into every appearance of color. These factors are: the light which illuminates the sample the object itself which is seen and the eye which transmits to the brain the sensation of color. The psycholo- gist may disagree with this and say that the mind may have a concept of color even in the absence of light. The physicist may disagree with this and say, that an object has color even though there is no observer present to discern it but without getting into these philosophical dis- cussions, let us examine these three factors more closely and see how they are related to the sensation of color. The importance of the illumina- tion is easily demonstrated. If a red lipstick is held in white light, the eye receives a sensation of red. On the other hand, if the red lipstick is viewed in green light, the red lip- stick will appear black. Illumina- tion is, therefore, an important fac- tor in the discernment of color. Even so-called white light is not always white, and daylight itself cannot be taken as a standard white * Presented at the May 15, 19•,6, Meeting, New York City. 54 light, because it is so variable. Light from the north sky is very blue in color compared with light from the southern sky. Direct sunlight is quite yellowish in color, but as sunlight passes through the atmosphere, some of the light is scattered sideways. When a sam- ple is viewed with north sky light, the illumination is not direct sun- light, but is the sideways scattered radiation. This sideways scattered radiation is quite bluish in color, and in fact it is this which gives the blue appearance to the sky. It is . thus possible for two samples to look alike on the south' side of the building where they are illuminated by direct sunlight, but to appear quite different when they are viewed by north sky light on the north side of the building. The color of,day- light is not only variable depending upon whether the north or south sky is used to illuminate the sample, but also it varies from day to day because of cloudiness and other fac- tors in the atmosphere, and it varies over one day from morning to night. If one wishes to make any scientific calculations on color, as viewed in daylight, it is necessary to define what is meant by daylight. This

COLOR MATCHING IN THE COSMETIC INDUSTRY 55 has been done. The International Committee on Illumination in 1931 adopted a standard kind of white light which they call "Illuminant C." This illuminant is similar to a mixture of north sky light and sun- light, and is a definite, fixed kind of light. Cosmetics are observed not only outdoors, but also, and perhaps even more importantly, under different kinds of artificial illumination. Modern lighting engineers have gone ahead with the development of tungsten filament lamps, fluorescent lamps having different phosphors in the coating, and gas or vapor lamps, such as the neon lighting signs. Added to this complexity are the various color effects introduced by means of colored filters placed over lights, particularly in places of amusement. Of all these artificial sources of light, only one has been defined that is a tungsten light. Illuminant A was chosen by the International Committee on Illumi- nation and this is a standard tung- sten light substantially. The man responsible for formulating the color of a cosmetic therefore, has to con- sider the attractiveness of his prod- uct under all these different kinds of illumination. The complete specification of an illumination consists of a distribu- tion curve showing the relative energy of the light as a function of its wave length. When white light is passed through a glass prism, the white light is broken up into the different spectral colors, which .are the familiar rainbow colors, and the intensity of each kind of light is the spectral distribution curve. Since these spectral distribution curves are difficult to speak about, there has been a simplification introduced with the concept of color tempera- lure. If an iron poker is placed in a furnace, as it warms up it will first become a dull red color, and as it gets hotter and hotter, the color will progressively change from a red to a yellow to a white, and finally to a bluish white color. This change in color of a so-called black body as it reaches differont temperatures some- what parallels the variation in apparent color of daylight under different conditions, and closely parallels the tungsten filament light at different voltages and therefore the concept of color temperature has been used to specify the color of an illuminant. For instance, it may be said that the north sky at a par- ticular time has blue color which is similar to the color which a black body would have if it were heated to a temperature of 10,1300 ø Kelvin. It is approximately true to say that the color temperature of the north sky is 10,000 ø Kelvin on this par- t•cular day. This does not mean that the temperature in the sky is actually 10,000 ø Kelvin, but it really means that the color coming from the sky is similar to the color which would come from a black body at a temperature of 10,000 ø Kelvin. Fluorescent light differs still more in its spectral distribution from the spectral distribution of black body light at any tempera- ture. The concept of color tern-