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Dubey says that because of asphalt's thermoplasticity, it needs to be applied when the temperature is 50˚F or higher and contractors can't risk applying it in lower temperatures.

"Thermoplasticity is the temperature at which a material becomes fluid," Dubey says. "Asphalt-based sealer requires higher temperatures to become fluid than does coal tar sealers. It requires higher temperatures for asphalt particles to come together to form a continuous film, which is why asphalt sealers can't be applied unless the temperature is at least 50˚F. If it's not at least 50˚F the film formation will be jeopardized, the film won't form properly, and it will wear out prematurely."

Dubey adds that asphalt-based sealers can't be diluted more than 25% with water and they also dry slower than coal tar sealer. He recommends that, unless weather conditions are ideal, and particularly in spring and fall, contractors should allow as much time between coats as possible, 8 hours at least but 24 hours is preferable.

"That's something contractors need to be aware of because they should factor it into their bid," he says. "A delay that long will require a second trip to the jobsite, which is something contractors using coal tar sealers are not used to."

He says contractors need to make their customers aware of the additional time, too, as customers used to one-stop contractor visits or night time sealcoating might now be forced to consider other schedules to get the maximum performance out of the asphalt-based sealers.