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

Content: A mixture in which two immiscible substances, like oil and water, stay mixed together thanks to a third substance called an emulsifier. The emulsifier is usually something like a soap, whose molecules have a water-soluble end and an organic-soluble end. The soap molecules form little balls called micelles, in which the water-soluble ends point out into the water, and the organic-soluble ends point into the inside of the ball. The oil is stabilized in the water by hiding in the center of the micelle. Thus the water and oil stay mixed. 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.