A number of authors have written about scale-up processes for personal care products. One commonly referenced article by Dickey describes the importance of consistent tank geometry and provides a few approaches to calculating scalable mixer speeds.1 Similarly, Yacko has presented on mixing and heat transfer considerations, as well as specific parameters and variables for cosmetic emulsions.2 His work includes the often overlooked variable of shear on the physical properties of an emulsion as it is compounded and filled.
For those interested in modern technology for scale-up and mixing, simulation softwarea has evolved to an amazing degree to allow engineers to vary the parameters around different mixing systems and predict the results. These systems include models for turbulent flow (low viscosity liquids), laminar flow (high viscosity, non-Newtonian fluids such as emulsions), and combinations of different and multiple impellers on the same shaft, including the commonly used anchor mixer with side scrapers. Newer softwareb has even added a module for high shear devices such as homogenizers and mills for calculation of shear rates, pumping capacity and power consumption or torque.