The subjective assessment of the consistency of materials in relation
George W. Scott Blair · 1966
1tlr01si--In all traditional, and even in some modern industries, the of materials and products are assessed by experts handling them. This is not in itself a bad thing but experts are becoming increasingly difficult to find and it is useful both for the craftsmen themselves and for those working in their absence to be able to compare such subjective assessments with physical measurements and chemical analyses. This paper is concerned with one group of properties commonly called consistency. One must first ask whether the sensations perceived by the experts are themselves quantitatively measurable and, if not, how do we regard the judgements which they are undoubtedly able to make? A second question follows: By what combinations of stresses, strains and times do people assess consistency when they squeeze materials by hand ? Are such combinations dimensionally similar to those which we use to define such physical as viscosity and elastic moduli? What mathematical and statistical techniques are required to describe the judgements offered ? Finally, the implications of psychorheology to the practical chemist or physicist working in a traditional industry are discussed.