New Coating Protects against Wildfire


Approaching wildfires have typically left no options for vulnerable homes in their path. Now, researchers say, they have one.

A new temporary fire-retardant coating sprayed on a home exterior at the last minute may buy the structure critical time to prevent its destruction from a forest or brushland wildfire, according to scientists at the U.S. Department of Agriculture.

The experimental gel coating was developed by plant physiologist Gregory M. Glenn and colleagues at the Agricultural Research Service (ARS), USDA's chief intramural scientific research agency.

The new fire-retardant gel may offer better, less expensive protection than others of its kind, the team says in a research announcement.

ARS is now seeking a patent for the product.

Clay and Corn Starch

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, according to ARS.

Depending on the circumstances, that timeframe might be long enough to save a house, says Glenn. In a best-case scenario, a homeowner would need only to wash the coating off the house after the fire.

Tests and Results

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 seven by seven inches by 3/8-inch thick. The team then coated all but the "control" squares with the experimental gel, a commercial gel, or other formulations.

ARS researchers
ARS / Delilah Wood

Researchers Artur Klamczynski (left) and Greg Glenn prepare to conduct burn tests of siding coated with their experimental fire-retardant gel.

In several tests that followed, the experimental clay-and-starch gel outperformed the other coatings, the team said.

Drying tests, for example, "showed that the gel kept its moisture longer, which is an important quality in a fire retardant," according to ARS.

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

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 stay in place and thus shield the siding.

'Promising, All Natural'

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

Although neither sodium bentonite clay nor starch are new to firefighting, ARS says its team is the first to combine these materials in a fire-retardant coating and the first to analyze such a coating's effectiveness.

Glenn collaborated with co-workers Bor-Sen Chiou, Artur Klamczynski and Zhongli Pan at ARS' Western Regional Research Center in Albany, CA, and with former ARS researcher Gokhan Bingol.

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


Tagged categories: Coatings Technology; Exterior Wall Coatings; Fire; Flame-retardant coatings; Health and safety; Research; Residential Construction; Specialty functions; Walls

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