Behind the Lotus EffectTM
A lotus is an aquatic plant a water lily of sorts that is native to Asia and Australia. It sports very large, heart-shaped green leaves and offers a beautiful, pink, fragrant bloom. The plant is very photosensitive at night, the lotus closes and sinks under water; at first dawn's light, the flower re-emerges and blooms again. Due to this cycle, the lotus has played a historic role in Egyptian, Greek and Asian mythology and art, symbolizing the sun, creation and rebirth.
In watching this curious plant, Wilhelm Barthlott, a botanist from the University of Bonn in Germany, discovered two additional facts about this process. First, the leaves are superhydrophobic, meaning that water beads on the surface and will eventually roll off without soaking into the skin. Even more important, the plant has a self-cleaning process. The waxy makeup of the leaves' surface not only resists water, but encourages the water droplets to remove dirt from the leaves as it rolls off. Every morning, when the plant rises from the murky pond, the leaves are cleansed by the water, leaving nothing behind but a clean, dry surface. Barthlott named this phenomenon the "Lotus Effect" and now holds the trademark and patent on the chemical process.
From Botany to Buildings
Naturally, the Lotus Effect immediately caught the eye of chemists across the world, who have since created laboratories and studies on how to mimic this occurrence in man-made products. Although scientists still have a long way to go in creating true superhydrophobic goods or a transparent application, the desire to create self-cleaning products from coatings for shoes, films for windows, eyeglasses and camera lenses, and applications for building walls is slowly becoming a reality.
In Europe, they've had Lotus Effect exterior paints since 1999, which have been used throughout all sectors of the building market. While the North American construction industry has had little to no access to these products, the wait is finally over.
Paint the Town Red
In June 2005, Sto Corp of Atlanta introduced LotusanTM, an exterior paint that can be applied to masonry, stucco, fiber cement and EIFS. And just like the lotus plant, the paint provides similar water resistant and self-cleaning properties water rolls right off and takes much of the dirt with it. Sto representatives stress that they are not pushing Lotusan as a waterproofing product, although studies show it will keep the water on the surface and prevent infiltration; they are focusing more on the cleaning action of the product.
"Cleaning will be done less often and will last longer than what they're doing now," says Bryce Brandon, market manager of Sto Corp. "It's not going to be a 'never have to clean' situation; however, if you're in an extreme environment and you have to clean every two or three years with standard surfaces, then maybe you can go five years before you have to clean with this product."
Buildings that have been treated with the proprietary primer and two coats of Lotusan remain dry and attractive longer particular advantages for building walls that are exposed to severe weather effects. The new surface technology also reduces the risk of attack by microorganisms. Algae and fungal spores are either washed off or are unable to survive on a dry and dirt-free exterior. This was confirmed in a three-year study, which found that the level of germs on a surface coated with Lotusan was 90% lower than that on a surface coated with a conventional paint product.
One unfortunate drawback with the current technology is the inability to provide the product as a clear coating, which scientists say is not likely to be produced, at least not anytime in the near future. However, many owners and builders may overlook this fact as a mere nuisance given the product's capabilities and attractive finish. Lotusan has a smooth, flat matte surface and is available in any of Sto's 38 classic colors (with limitations, custom color matching can also be used).
"Aside from the added characteristics, it's the same as any paint really," Brandon says. "It applies the same, cleans the same, and strips off the same way."
Contractors need to be mindful of the mortar condition and correct any issues before applying Lotusan to brick, block and stone masonry.
"The only technical issue that we might be concerned with is recoating old masonry jobs where the mortar joints are getting old or crumbling," warns Brandon. "As long as the mortar joints are solid, it'll work really well."
Like flashing, vents, vapor barriers and other types of moisture management products, Lotusan should not be considered a sole solution to the age-old masonry water infiltration problems. Mason contractors should still pursue using the appropriate mix of products in their moisture management strategy. However, as a paint product, Lotusan offers an interesting option to add to your arsenal.
"We believe that it's going to outperform anything else," says Brandon.
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