j. Soc. Cosmet. Chem., 40, 141-149 (May/June 1989) Perceptual evaluation of shaving closeness MIKLOS M. BREUER, RAYMOND L. SNEATH, CARRIES. ACKERMAN, and STEVEN J. POZZI, The Gillette Company, Boston, MA 02106. Received November 23, 1988. Presented at the Annual Meeting of the Society of Cosmetic Chemists, New York, December 1988. Synopsis A sensory perception technique has been developed by which the relative shaving closeness provided by a variety of shaving products can be easily compared. Judges who have received a minimum of training are asked to determine, by way of tactile and visual evaluations, whether each side of a shaved face is smooth or rough. By comparing the frequency of the smooth response as a function of time after the shaving process was completed, the duration of the smoothness perception and, thence, the shaving closeness provided by two shaving products can be compared. A statistical model has been developed by which these data can be analyzed. INTRODUCTION Recently we have described a novel method for measuring beard hair removal efficacy of shaving systems using image analysis as a measuring technique (1). Beard hair removal efficacy is, however, only one factor that contributes to the consumer evaluation of shaving preparations. An important attribute by which consumers judge the efficacy of shaving systems is the closeness of the shave. Unlike hair removal efficacy, which is quantitatively measurable by objective physical methods, closeness of shave is a "sub- jective" sensory quantity, the magnitude of which will depend on a number of "objec- tive" contributing factors: hair removal efficacy, the lubricity imparted to skin, lack of irritation, etc. Our long-term objective in this research program is to elucidate the relative contribu- tions of the various physical quantities to the perception "closeness of shave." To achieve this goal, we first need a method that is capable of measuring in a reproduc- ible and quantitative way the intensity of the sensory stimulus that shaving closeness evokes. The current report describes our endeavors to achieve this goal and gives details of a novel technique that we have developed for measuring the perceived intensity of "shaving closeness." 141

142 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RESEARCH APPROACHES The general principles of measuring sensory quantities have been described in a number of publications (2,3) and will not be repeated here. In principle, two approaches are possible for the gauging of perceived shaving closeness: self evaluation of shavers using a suitable measuring scale (for instance, magnitude sealing) (2,3) or evaluation of the closeness of the shave by independent judges. Self-evaluation methods for assessing shaving closeness have been developed in the past and are in routine use for evaluating the efficacy of various shaving systems and toiletry shaving preparations. A failing of self-evaluation techniques is that it is often difficult to conceal from the shaver the identity of the shaving product to be tested (e.g., com- paring a shaving foam with a shaving brush product), a fact that might prejudice the judgment of the shaver. Furthermore, it is also unclear whether during self evaluation shavers evaluate the actual, final state of the shaved face, or rather judge the shaving process itself. While both the state of the shaved face (i.e., the quality of the shave) and the sensations experienced during the shaving process are important factors that con- tribute to the consumer assessment of the efficacy of the shaving product, the relative importance for product acceptability is unclear. Furthermore, since improving the final outcome of the shaving process (e.g., the smoothness and the appearance of the face) and the perceptions of the sensations which are experienced during the shaving process (e.g., pulling of beard hair, pain, and nicks and cuts) most probably require different technical approaches, the availability of a measuring technique that is capable of evalu- ating one of these quantities independently might yield important information for fu- ture product development. By using independent judges who assess the quality of the shaved face after the shaving process has been completed, it is possible to gain informa- tion complementary to that which is obtained by self evaluation. We explored three methods for utilizing independent judges for assessing shaving close- ness. Five female judges were employed who did not have any prior training. Although trained judges are often required to perform valid perceptual evaluations, we attempted to limit training so as to make our technique applicable to a wider range of laboratory environments with limited manpower resources. Shaving closeness is a complex at- tribute which is difficult to define accurately. It is generally used to describe the quality of shave when it is measured by self assessment. In order to obtain a better defined result the judges were asked in these studies to evaluate the smoothness of the face after shaving using tactile and visual perceptions. We assumed that the duration of the smoothness perception after shaving would serve as a measure of "closeness" of the shave. MEASURING SHAVING CLOSENESS ON A CATEGORY SCALE USING SPLIT FACE SHAVING PROTOCOL In this experiment our objective was to establish whether a panel of independent judges could measure perceptible differences in shaving closeness using a seven-point category scale. The shavers (6 to 10) in this study used two different products (Products A and B). Previously objective measurements using our image analysis technique (1) had shown that the use of Product A allowed for the removal of significantly longer beard fibers than did the use of Product B. The average whisker length removed using Product A was 2% greater than that removed by Product B. The difference was statisti-