TISSUE SOFTNESS EVALUATION BY MECHANICAL STYLUS SCANNING

A mechanical stylus surface analyzer (MSSA) system and the correspondi ng software were used to conduct standard surface analysis procedures. The MSSA instrumentation measures surface characteristics of soft bat hroom tissue products. This paper describes the applicability of MSSA and how human tactile response may be modeled through characterization of surfaces. The concepts of passive and active touch as related to h uman perceived softness are reviewed. In particular, parameters pertin ent to these kinds of tactile exploration are mentioned, as well as ho w they can be used to build a better model of human tactile response. A novel frequency analysis parameter called the frequency index for ta ctile sensitivity (FITS) is based on tissue paper surface analysis res ults from MSSA and provides the basis for the human response model. In cluded is a review of subjective human softness evaluation data for se lect tissues gathered to represent actual human responses. The MSSA an d optical image analysis (OIA) data were collected on the same tissues , and the FITS parameter was found using MSSA. Also, MSSA data were us ed to reproduce an old standard parameter for evaluating tissue softne ss called the human tactile response (HTR) index. Since it is not poss ible to exactly reproduce HTR, the reproduced parameter calculated in this study is called HTR equivalent (HTR}EQ). Finally, standard deviat ion of luminance (SDL) and loosely bonded surface fibers (LBSF) parame ters are determined for select tissues using OIA. Correlation results of the human data with FITS, HTR}EQ, SDL, and LBSF are discussed; FITS correlates best with the human response data and, together MSSA and F ITS, has the ability to model human response to the softness of tissue paper products.