Surfactant leaching, also known as exudation or weeping, causes the appearance of sticky brown residue or spots on paint.
Surfactants are necessary ingredients of latex paint. These water-soluble components
migrate over time to the surface of the paint and eventually evaporate.
When newly applied latex paint is exposed to high moisture or humidity while it's drying and/or curing, the surfactants can rise prematurely to the film's surface, producing a brown residue or splotches. Surfactant leaching frequently shows up in bathrooms and other humid environments as brown stains on ceilings or walls.
While unattractive, surfactant leaching does not harm the coating.
What Causes Surfactant Leaching?
- Cool, humid conditions can draw the surfactants to the surface before the paint thoroughly dries.
- Surfactant leaching is common on outdoor surfaces, as well as in bathrooms, where moisture condenses on walls.
- Tinted colours are more prone to surfactant leaching, due to the extra surfactants
and glycols in the added colourant.
How to Remedy Surfactant Leaching
- Rinse the surface with water or wipe with a damp cloth as soon as you notice stains. You may have to clean the area periodically as leaching occurs over time.
- On exterior surfaces, normal weathering will usually remove surfactant stains naturally. Stains can accumulate, however, on surfaces shielded from the elements.
- Stains must be removed before you repaint.
How to Prevent Surfactant Leaching
- For interiors, try to make the environment as dry as possible during and after paint application.
- In bathrooms, allow the paint to dry thoroughly before using the shower.
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