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Tech Flash compliments of Coronado Paint Company

Surfactant Leaching is the concentration of water-soluble ingredients on the surface of latex paints. It creates a blotchy, sometimes glossy appearance with a brownish or tan cast.

All latex-based paints contain some water-soluble ingredients, which are required for color, stability, and ease of application. Usually these water-soluble ingredients either evaporate, or they leach from the paint due to rain or dew. If latex-based paint is applied during cool and damp conditions, or when the temperature falls within 5° of the dew point, the drying is retarded and the ingredients come to the surface before the paint has had a chance to dry. Surfactant leaching can also be caused when dew or other moisture dries on the painted surface shortly after the paint has dried. Paints that are tinted using universal colorants are more prone to this condition than white or ready mixed colors because of the surfactants and glycols present not only in the paint, but also in the colorant. In most cases, surfactants come out of the paint film slowly and are washed away undetected. Surfactants are not part of the paint film and their migration from the film does no harm to the paint film whatsoever.

To prevent surfactant leaching, avoid application of latex-based paints in late afternoon and/or if cool, damp conditions are expected overnight.

Surfactant leaching can have a serious effect on the appearance of the project.
If surfactant leaching is present in the first days after application, most often the water-soluble ingredients can be easily removed by simply washing the surface with a mild solution of soap and clean fresh water and rinsing with a fine mist from a garden hose. In some cases this process will not remove the residue. In this case, the residue should weather off in about a month.

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* Pro Tips *
Surfactant leaching is always a possibility when painting in the cooler months. Paint takes much longer to cure, exposing the uncured paint film to a greater chance of moisture exposure.