2. Making an emulsion

Emulsification generally involves two successive stages: firstly, a dispersion-mixing stage, known as "pre-emulsification", which simply suspends droplets of the dispersed phase in the continuous phase (droplets of the order of 100 µm), followed by a "homogenization" stage, the aim of which is to reduce droplet size so as to give the emulsion the required properties and stabilize it. These two operations are carried out in stirred tanks or in pipes fitted with tools called "dispersers" and "homogenizers" respectively.

The various stages in the manufacture of an emulsion are shown in figure 1 , where we can see the large number of "process" variables to which we must add those of formulation: we have here a global overview of the complexity of the problem. The key stages are discussed...