NACREOUS AND INTERFERENCE PIGMENTS 177 reflection, and transmission, using a Leres Trilac goniospectropho- tometer. Nacreous luster is most nearly described by specular reflectance, but the total visual effect of a particular nacreous pigment depends in addition on diffuse reflectance and transmittance. The appearance of one nacreous pigment cannot be duplicated by a chemically different nacreous pigment since the specific combination of these factors is de- pendent on the refractive index. The other properties which determine nacreous behavior are platelet dimensions and the smoothness of the platelet surfaces. Specular reflectance increases with increasing nacreous pigment con- centration up to a certain point. Thereafter, further increase in con- centration leads to a decrease in specular reflectance. The maximum specular reflectance achievable with a given nacreous pigment is a measure of its inherent nacreous luster. Interference pigments are examples of nacreous pigments which are color-producing in addition to having the usual nacreous pigment characteristics. These pigments exhibit two kinds of goniochromaticity, or change in color with varying angles of illumination and viewing: (a) the reflection color, which is seen at specular reflection, moves to lower wavelength with increasing angle of incidence, as was shown by spectrophotometric curves at -- 15 o / 15 o and --45 o/45ø (b) with the pig- ment on a white background, measurement at a specular angle exhibits the reflection color, while measurement at a diffuse or nonspecular angle reveals the complement of the reflection color, or transmission color. (Received October 26, 1970) REFERENCES (1) Greenstein, L. M., Nacreous pigments and their properties, Proc. Sci. Sect. Toilet Goods Ass., 45, 20-6 (May, 1966). (2) Greenstein, L. M., and Miller, H. A., The properties of nacreous pigments, Tech. Pap., Ann. Tech. Conf., Soc. Plast. Eng., XIII, 1121-32 (May, 1967). (3) Greenstein, L. M., Nacreous Pigments, in Encyclopedia of Polymer Science and Technol- ogy, Vol. 10, Interscience Publishers, New York, 1969, pp. 193-211, 215-9. (4) Hunter, R. S., High gloss measurements, Off. Dig., Fed. Soc. Paint Technol., 36, 348-56 (1964). (5) Hemmendinger, H., and Johnston, R. M., Goniospectrophotometric color measurement: use of the Trilac goniospectrophotometer, paper presented at the 1st AIC Cngress, Color 69, Stockholm, June, 1969. (6) Billmeyer, F. W., Jr., and Davidson, J. G., A research spectrogoniophotometer, ]. Paint Technol., 41, 647-53 (1969). (7) Johnston, R. M., Geometric metamerism, Color Eng., 5, 42-7, 54 (1967).

178 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Society of Cosmetic Chemists Medal Award to Samuel Zuckerman The Society of Cosmetic Chemists has presented its 1970 Medal Award to Dr. Samuel Zuckerman, Vice President and Director, H. Kohn- stamm g: Co., Inc., New York City. The Society's Medal Award, its highest honor, is presented annually to the scientist or individual who has, over a period of years, contributed significantly to the advancement of cosmetic science, cosmetic scientists, and the cosmetic industry. The award was formally presented at the December 1st luncheon session during the Society's annual meeting at the Americana Hotel, New York City. Mr. Paul I.. Kohnstamm, President of H. Kohnstamm g: Co., Inc., served as Eulogist. LeIt to right: Eulogist Mr. Paul L. Kohnstamm Medalist Dr. Samuel Zuckennan and the Society's President, Mr. Charles Fox