Surfactant Leaching Explained
Preventing Leaching Water Marks 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
Dark paint colors contain more colorant, leading to longer 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 hrs. 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 like siding.
Rain, humidity, ground-level dew, frost, and home sprinkler systems are the leading causes of 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.
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 will 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 UV.
Interior Bathroom Leaching & Watermarks
Interior wall paint can leach and 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 & Remove Surfactant Leaching
When surfactant leaching happens, the chances of removing the residue is higher in the earlier stages before the surfactants dry or stain the surface.
- Draw hot water into a sink and add a small amount of dish soap. Wipe the surface using a microfiber cloth and wipe again using a clean damp rag.
- For exterior leaching removal, use a pressure washer or garden hose. In more extreme cases, wiping the areas with a rag is required.
- Removing paint surfactants may require cleaning the surface more than once. Although, if the stains are not removable, the surface must be primed and repainted. Priming the entire surface will prevent the stains from resurfacing.
Preventing Paint Leaching
One of the beauties of house painting is that there’s little that can happen that can’t be fixed, but some things are costly to fix and can be avoided.
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.