Abstract All variables capable of altering the physico‐chemical formulation, including temperature, are included in a generalized concept known as the hydrophilic–lipophilic deviation (HLD), which measures the departure from the reference state at which the surfactant–oil–water system exhibits Winsor III three‐phase behaviour. The general phenomenology representing the emulsion properties (type, stability, viscosity, drop size) can be qualitatively charted in a three‐dimensional map, where each region exhibits definite features. Travelling across the map from one region to another corresponds to modifications in formulation, composition and stirring along a path which can describe the protocol of change in an industrial process dealing with emulsion making, inversion or reworking. Six different path cases, labelled as unit operations, emerge from a systematic categorizing, and allow the interpretation of complex industrial processes such as crude oil dehydration, or the manufacturing of paint, cosmetics or heavy hydrocarbon emulsions. © 2003 Society of Chemical Industry