616 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 4. Repetitive photography of a site on Caucasian skin. Recorded with (A) a Kodak CC50C-cyan filter (B) a yellow filter equivalent to Kodak 81C a positive replica is made by melting polyethylene pellets* in vacuo at 180øC. After shadowing with Au-Pd to a thickness of 150 A as was previously de- scribed (26), metal coated 9 mm punches of the polyethylene replicas are examined with a JEOL JSM-2t instrument at 30 to 3,000 X magnifications with accurate reproduction of details and greatly enhanced depth of field compared to conventional .light microscopy. Unmodified and solvent-extracted human skin in vivo have been examined in this manner (8). Impressions are obtained from the backs of panelists' hands before treatment in order to obtain control photographs. Half of each hand is then extracted with diethyl ether for 60 sec. The hands are dried and water-soaked with a damp flannel patch for i h. Following removal of the patches and blotting away the excess water with a paper tissue, Silastie* negative impressions are taken of the ether-water and water-only soaked areas. Together with the adjacent samples derived from unmodified skin, positive polyethylene casts are taken of each of the two extracted skin specimens. •Union Carbide, Chemicals and Plastics Division, New York City, NY 10017. J'JEOL U.S.A. Inc., Medford, MA 02155. *Dow Corning Corp., Midland, MI 48640.

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