Yield stress measurements for QC: viscometers versus rheometers

In this short communication paper, we present a comparative analysis of the methodologies used on Brookfield viscometers to determine yield stress to those used on high-end stress-controlled rheometers. This communication specifically focuses on the test most commonly used in industrial rheology, i.e., stress overshoot tests on Brookfield viscometers and stress ramps on the rheometers. Tests of commercial products, namely toothpastes and sunscreens are considered. It is demonstrated that the yield stress values obtained via the manufacturer’s recommended viscometer protocol overestimate the yield stress determined by a controlled-stress rheometer utilizing a stress ramp test. However, we established statistically significant correlations between the two measurements, enabling the prediction of the yield stress using the simpler, low-cost Brookfield viscometer as a predictive rheological tool.