Abstract Slurry rheology is an important property in many mineral processing systems, but its influence is not well understood and it is rarely incorporated into process design, analysis or optimisation. One reason for this is the difficulty of measuring rheology (particulary in plants) and of interpreting the output of such measurements. This paper presents a new procedure for obtaining a full shear rate-shear stress flow curve for unstable slurries using the single bobbin Debex on-line viscometer. It is based on the use of a calibration algorithm which incorporates a correction for turbulent flow in the measurement vessel. It is shown that torque coefficients data from a variety of Newtonian fluids and non-Newtonian slurries fall on a single curve, and it is suggested that this calibration curve (the “TC curve”) is characteristic for a particular instrument configuration. In principle, it can be easily determined using Newtonian fluids alone. It is shown that the Debex on-line viscometer gives flow curves very similar to a conventional laboratory viscometer when this procedure is applied.