Surfactant Leaching Explained: Preventing Watermarks on Paint Finishes

Surfactant leaching happens when uncured water-based paint is prematurely exposed to excessive moisture, leaving brown, milky, or oily streaks, circles, or watermarks. While surfactant leaching has no adverse effect on the durability of the paint, it can be unsightly and is common with thick paints and darker colors.

Surfactants are additives that enhance the performance of the paint, improving dry times, leveling, ease of use, and more. Each manufacturer has proprietary formulations, some more resistant to leaching than others. Professional house painters should be able to recommend paint lines that mitigate leaching, offering a streak-free surface.

Surfactant Leaching Using Dark Exterior Paint Colors

Darker colors contain more colorant, leading to longer paint dry times and more challenging paint applications. Since dark colors take longer to cure, they are more prone to surfactant leaching.

When painting the exterior of a house, uncured paint films are often exposed to low moisture levels within the first 24 hours of application. While low moisture levels are expected and typically will not cause any issues, dark colors reveal surface imperfection the most.


As surface-level moisture builds, surfactants are naturally drawn out. Exterior paints that dry quickly and have fewer additives will resist leaching best. Moisture-resistant exterior paint should be used on shutters, doors, and larger surfaces such as exterior siding.

Painting in rainy and humid conditions is the leading cause of surfactant leaching. However, ground-level dew, frost, and home sprinkler systems can lead to minor surfactant leaching. Atmostoshperic moisture is out of anyone’s control and cannot be avoided. So, the surface type, paint color, and weather must all be considered when choosing exterior paint that will resist these elements.

In our experience, Sherwin-Williams Resilience performed the best in resisting leaching. Since it has now been discontinued, SW Latitude is the next best.

Resolving Thick Exterior Paint Leaching Issues

Increased surfactants in almost all thick exterior paint coatings enable effortless paint applications.

Thick paint is prone to leaching and is a drawback, but lighter colors make the marks less visible. Light colors allow painters to use thicker paints without the concern of visible leaching. Thick and light-colored trim will protect wood trim better and naturally resist paint fade caused by UV.

Interior Bathroom Leaching & Watermarks

Interior wall paint can leach, which is a common issue in bathrooms. One of the most common ways leaching presents itself inside is through oily streaks and discoloration.


It’s crucial to prevent uncured paint from being exposed to high humidity, heat, and moisture. Bathroom-specific paints are formulated to dry faster and cure harder to resist the effects of surfactant leaching.

Ways to Fix Surfactant Leaching

When surfactant leaching occurs, the chances of removing the sticky or oily residue are higher in the earlier stages before surfactants dry and have a chance of permanently staining the surface.

Removal Steps:

  1. Draw hot water into a sink and add a small amount of dish soap.
  2. Wipe the surface using a microfiber cloth and wipe again using a clean, damp rag.
  3. For exterior leaching removal, use a pressure washer or garden hose. In more extreme cases, wiping the areas with a rag is required.
  4. Removing paint surfactants may require cleaning the surface more than once.

Repainting Process:

  1. The surface must be primed and repainted when stains from surfactant leaching are not removable.
  2. Priming the entire surface will prevent the stains from resurfacing.

Preventing Paint Leaching

The beauty of house painting is there’s little that can happen that can’t be corrected, but cleaning or repainting surfaces due to water spots can be costly and is avoidable.

The best way to prevent surfactant leaching is first to know what it is and what causes it. Secondly, product knowledge is critical to maximizing interior or exterior paint performance.

Raleigh, NC, gets a lot of rain during the spring and summer months, and as exterior house painters, knowing how to prevent and identify leaching is vital to professional results.

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