REPLICATION OF SKIN 111 steps. The material was allowed to cure for a minimum of eight minutes from the start of the mix. (Variations in temperature will affect the work and set times. Accordingly, the replica was not to be removed from the skin until it was firm, resilient, and non-tacky.) The replicas were stored in Petri dishes to protect the surface. It is suggested to delay making the epoxy impression for 60 minutes. To make a positive impression for the negative replica, Spurr's low-viscosity embedding medium was prepared according to directions contained in the kit. The positive replica was generated using a circular mold that was 2-cm in diameter and 0.5-cm deep. The mold was filled with the epoxy resin using a disposable pipet. The negative impression was precut to fit in the mold. A drop of resin was applied to the replica and carefully spread to wet the surface. The negative was gently placed into the filled mold, surface- down, onto the epoxy. (The Reprosil will float and can be cured in this manner.) The molds were placed in a large glass Petri dish and cured at 65øC in an oven in a fume hood for a minimum of eight hours. WARNING: Do not use any containers made of polystyrene with the Spurr's embedding medium as the polystyrene is incompatible (i.e., the Spurifs medium will dissolve the polystyrene). After curing, the samples were removed form the molds upon cooling to room tem- perature. The positive impressions were trimmed to remove excess epoxy material by scoring the undersurface and cutting from the opposite side. The Reprosil was carefully peeled away from the cleaned epoxy replica. The positive impression was mounted on a one-inch, aluminum scanning electron microscope (SEM) stub with double-sided ad- hesive. The specimen was then sputter-coated with approximately 25 nm of Au/Pd. iNSTRUMENTATION The positive impressions were examined with a Hitachi S-520 SEM operating at l0 KV, 15 mm working distance, and a 15 ø tilt towards the detector. DIMENSIONAL STABILITY OF THE REPROSiL NEGATIVE IMPRESSION An impression of an area of approximately 30 mm 2 on the inner left forearm was made as described above. A positive impression was produced from the same Reprosil mold on days 0, 77, and 81. EFFECT OF REPLICATION ON THE SURFACE OF THE SKIN Impressions of an area of approximately 30 mm 2 on the inner left forearm were made in series at 30-minute intervals. Reprosil impressions of the sole of the foot were made at 0 and 30 minutes. REPLICATION OF FINE, DELICATE STRUCTURES An impression of an area of the forearm that contained several hair follicles was made as described above. In addition, replicas of the leaves of two plants, velvet leaf and coleus, were also made.

112 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ARTIFACTS The nature of the globular structures present on the surface of the skin was investigated by replication of a variety of materials, both living and inert. Substrates investigated included a woven fabric, leather, the palm of the hand, and the leaves of two plants: velvet leaf and coleus. APPLICATION TO THE DETERMINATION OF THE FATE OF A POLYMER ON SKIN The fate of an experimental polymer contained in a facial lotion was investigated in this study. Collection of the data set required five days, allowing one day for the skin to recover between each set. The following procedure was used on each of the test days (Day 1, Day 3, and Day 5): One hour prior to testing, the face was washed with water to remove excess salts and debris. A skin replica was obtained of the test area (forehead) before treatment (t = 0). The test region was wiped with a facial toner, and ten minutes later a second replica was obtained. The lotion was applied to the test area and a skin replica taken ten minutes after application and again at one (Day 1), three (Day 3), and five (Day 5) hours post-application. The skin replicas were prepared for SEM accoMing to the previously described method. 88075• 10FV X50.0 600um Figure 2. Topographical features of the positive replica cast from the same negative impression at Day 0 (a and d) Day 77 (b and e) Day 81 (c and f). G = globular structure P = pitting.