Viscosity (Part 1)

Abstract

This article reviews the standard specifications related to viscosity measurement, issued by ASTM, BSI, IP and other standard bodies, and their applications. The know-how embodied in these specifications is discussed in relation to knowledge recorded in the literature and some aspects of practical implementation and use are considered. It is shown that standards and calibration are well established for Newtonian liquids and viscosity measurement can be accurate and precise. But, for non-Newtonian fluids, the specifications give apparent viscosity, not absolute values; and even then the results, although they can be precise, are of uncertain accuracy. It is pointed out that information exists in the literature on the subject of absolute measurement of non-Newtonian viscosity but that it needs to be simplified and codified before it can be incorporated into standard specifications. Current work towards this end is referred to.