618 S. Nicholls, C. S. King and R. Marks (Permabond Staident Ltd) using the skin surface biopsy technique to reveal the ruptured internal surface of' the outer SC (1). Skin surface replicas Negative impressions of the skin surfaces were taken with standard Silflo impression material (J. & S. Davies, London). Positives of the skin surface were subsequently obtained from the 'negative' by covering them with DPX (R. A. Lamb, London) histological mounting medium (2). The negatives with DPX were then placed in a desiccator for 5 or 6 h or left overnight at room temperature before separating the 'positive' from the 'negative'. Scanning Electron Microscopy (SEM) Replicas and SSBs were mounted on stubs and coated with gold in a Polaron ES000, sputter coater, and examined in a Cambridge Stereoscan S2 scanning electron microscope at approximate magnifications of x 200 and x 1000. Macrophotography Photographs of the skin surface were taken using a 35 mm camera fitted with a 105 mm lens on a bellows attachment and an electric ring flash. Negatives were printed to give a final magnification of x 8. Skin furrow widths were measured with an eye piece graticule ( x 8) by taking measurements in each of five standard areas in the photographs (Fig. 1), and averaging the values for the five areas. Surface contour measurement of SSBs and replicas SSBs and replicas were examined in an apparatus (3) designed for measuring surface contours (Suffometer, Planer Products, Ltd). The surfometer employs a stylus to tra- verse a test surface, the contours of which are traced on moving chart paper. Skin surface biopsies (SSBs) The areas under the curves of the surfometer tracings were measured with a planimeter and the mean peak height calculated for a representative 10 cm length of trace. Skin surface replicas Only very thin DPX positives were suitable for surface contour tracing. When separated from the negatives they were left to harden at room temperature. The DPX positives were then fixed to glass slides and the surface contours measured in our surfometer. The area described by the surface contour in 10 cm length of trace was measured with a planimeter. (For the Oil of Ulay study (C) tracings of 8.5 cm length of trace were used and the total length of contour was also measured using a curvimeter). Ambient conditions Laboratory personnel acted as volunteers for the experiments. They were instructed to avoid activities (such as promotion of sweating as a result of exercise) which may have masked any effect due to the treatment. Relative humidity (RH) and temperature (øC) were monitered in the laboratory areas. (56 + 5•o RH 20.5 + 0.5øC).

Figure 1. Macrophotography. Measurement of skin furrow width in five standard areas of the photograph. Facing p. 618