As supported by Supplementary Figure this is because viscosity of the formulations has a pH dependency. Since the formulation's rheology was only characterised for the final sample product, the time for pH stabilisation on the last iteration of pH adjustment is taken and plotted against the formulation's apparent viscosity (taken as the viscosity at a shear rate of 10 s -1 ) in Figure . Apparent viscosity is used here, as the formulations are non-Newtonian, however this is referred to simply as viscosity from here on. A linear best fit line on a log-log plot shows us a power law relationship, supported with a high R 2 value of 0.92 that the optimal mixing time, t, is ∝ 𝜂 + where 𝜂 is the viscosity and a is some fixed exponent. The power-law relationship for the particular set-up used is shown in the legend of Figure , however, this is dependent on the dimensions of the stirred tank and speed of the stirrer. The general observation, however, is of greater significance, and guided us to implement dynamic control of mixing time on the pH robot. We were previously mixing all the formulations for 'as long as required' to homogenise the most viscous samples in the experimental set, where in fact the less viscous formulations could be well mixed much more quickly thereby reducing the experimental time further.