Mixture and mixture-process variable experiments for paint preparation applications

Many experiments in research and development in the paint preparation involve mixture components. These are experiments with mixtures in which the experimental factors are the components of a mixture and the response variable depends on the relative proportion of each components, but not on the absolute amount of the mixture. Thus the mixture components cannot be varied independently. A common variation of the mixture experiment occurs when there are also one or more process factors that can be varied independently of each other and of the mixture ingredients, to bring about a mixture process variable experiment. We discuss the design and analysis of these types of experiments, using flame-retardant coating formulation as an example. Goal of this paper is to encourage greater utilization of these techniques in paint preparation research and development.