It has long been believed that air temperature has a significant impact on spray coating finish quality, primarily due to its impact on the viscosity of the atomized paint particles. Millions of dollars are spent each year controlling the booth ambient environment based on this belief. One of the things that has always bothered us about this concept is the degree of seasonal variation that coaters experience. If the ambient temperature is being held constant year-round, why is it still necessary to have a summer blend and a winter blend? Since seasonal variations are, by their very nature, temperature related, it seems there must be something else at work here.