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United States Department of Agriculture

Agricultural Research Service

Temporary Coating May Help Protect Homes from Wildfires / September 3, 2013 / News from the USDA Agricultural Research Service
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Photo:  Forest fire beginning to burn trees.
Quickly spraying a home with an experimental fire-retardant gel coating developed by ARS scientists may give the structure temporary protection from a forest or brushland wildfire. Photo courtesy of the Federal Emergency Management Agency.


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Temporary Coating May Help Protect Homes from Wildfires

By Marcia Wood
September 3, 2013

Quickly spraying a home with a temporary fire-retardant coating may prevent it from being destroyed by a forest or brushland wildfire. An experimental gel that U.S. Department of Agriculture (USDA) plant physiologist Gregory M. Glenn and his colleagues in Albany, Calif., have developed might offer better, more affordable protection than other fire-retardant gels.

The experimental gel is made of sodium bentonite clay, corn starch and water. Preliminary tests suggest that a quarter-inch layer of the gel may protect wood-based home siding for up to 30 minutes.

Depending upon the circumstances, that timeframe might be long enough to save a house. In a best-case scenario, all that a homeowner might need to do after the fire is to wash the coating off the house, according to Glenn. He works for the Agricultural Research Service (ARS), USDA's chief intramural scientific research agency.

In preliminary research, documented in a 2012 article in Fire Safety Journal, Glenn and his coinvestigators cut planks of residential wood-based siding into squares measuring about 7 by 7 inches by 3/8-inch thick, then coated all but the "control" squares with either the experimental gel, a commercial gel, or other formulations.

In several of the tests that followed, the experimental clay-and-starch gel outperformed the other coatings. "Drying tests," for example, showed that the gel kept its moisture longer, which is an important quality in a fire retardant.

In "burn tests," siding coated with the research gel took longer to reach 392 degrees Fahrenheit, the temperature at which wood-based siding may begin to burn and char.

Other tests, in which the squares were positioned upright, demonstrated that the gel was less prone to sliding, technically known as "slumping," toward the bottom of the squares. The starch helped the coating to stay in place and, in so doing, to shield the siding.

In all, the California studies provide a foundation for more extensive tests of the promising, all-natural coating.

Although neither sodium bentonite clay nor starch are new to firefighting, the idea of combining these materials to form a fire-retardant coating is apparently a "first," as is the California team's detailed analysis of the coating's effectiveness.

Glenn collaborated with co-workers Bor-Sen Chiou, Artur Klamczynski and Zhongli Pan at ARS' Western Regional Research Center in Albany, and with former ARS researcher Gokhan Bingol. ARS is seeking a patent for the research.

An article in the September 2013 issue of Agricultural Research magazine highlights these studies.

Last Modified: 9/3/2013