Title: Emulsion and Latex Paint
Headings: Ask the Expert Question-and-Answer Archive

Content: www.psrc.usm.edu/
An emulsion is an unstable mixture of two incompatible liquids, such as oil and water. In the case of mayonaise, we add oil to egg yolk VERY slowly so that the "emulsion" won't break. In the case of a latex paint we add water to an organic resin, such as an acrylic in such a manner that the emulsion won't break. Since the resin is an oil-based product (ultimately derived from crude oil) we add a small amount of a coalescing agent that enables us to mix these two unlikely components. In the case of a latex paint the coalescing agent is compatible with the resin and is also compatible with water. For instance, household soap is compatible with grease and water. After we have mixed the latext paint, (which is an emulsion), we apply the paint and ideally allow the water to evaporate off before the coalescing agent can evaporate. Eventially the co-solvent (coalescing agent in a latex paint) evaporates and a uniform paint film is formed. I hope this helps
Best wishes,
Ron Joseph