The present invention relates to a method of monitoring a flow behaviour of mixed components, comprising: rotating a mixing impeller at a first speed N 1 in a mixing vessel accommodating the components to be mixed; determining a first quantity (formula I) at the first speed N 1 , wherein N 1 is the speed at which the mixing impeller rotates and P 1 is the power required to rotate the mixing impeller at the first speed N 1 ; decreasing the speed of the mixing impeller to a speed N 2 ; determining a second quantity (formula II) at the second speed N 2 , wherein N 2 is the speed at which the mixing impeller rotates and P 2 is the power required to rotate the mixing impeller at the second speed N 2 ; comparing the first quantity (formula I) and the second quantity (formula II) and detecting whether the difference between the first and second quantities is within a specified range to determine whether the flow of the components in the mixing vessel is a turbulent flow; determining the density ρ of the mixed components based on at least one speed N i for which the flow is determined to be turbulent by the formula (III) wherein ρ is the density, P i is the power required to turn the mixing impeller at the speed N i , N P,constant is the Power number for a used mixing system configuration, N i is the speed at which the mixing impeller rotates and D is the diameter of the mixing impeller; further decreasing the speed of the mixing impeller; determining the Power number N P,variable for at least one detected speed N j at which the flow is determined to be non-turbulent by the formula (IV) wherein P j is the power required to rotate the mixing impeller at the speed N j , ρ is the density previously determined based on N P,constant, N j is the speed at which the mixing impeller rotates, and D is the diameter of the mixing impeller; and determining the dynamic viscosity μ of the mixed components by the formula (V) wherein ρ is the calculated density, N j is the speed at which the mixing impeller rotates, D is the diameter of the mixing impeller, P j is the power required to rotate the mixing impeller at the speed N j and x T corresponds to a specified relationship between the Reynolds number for the used mixing system configuration and the determined Power number N P,variable . Further, the present invention relates to methods for detecting settled solids at a mixing impeller.