By Maria Medina

SACRAMENTO (CBS13) — Planes are expected to drop nearly 12,000 gallons at a time of fire retardant on the Rim Fire, which has expanded into Yosemite National Park.

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But what exactly is that orange stuff dropping out of planes, and what important role does it play in firefighting efforts?

The fire retardant starts in powder form, meaning all firefighters have to do is combine it with water to help stop the flames.

“There’s a big difference between fire retardant and water,” said Logan Maxim, a fire retardant specialist.

From the air, pilots watch the wildfire to see where it might be heading. The goal is to drop the retardant ahead of the flames. As the fire creeps toward the retardant, the fire is put out.

“So flame can’t pass through vegetation that’s been coated with retardant,” he said. “The flames will pretty quickly die out.”

Crews work fast to get the retardant in the air and onto a blaze. It takes this crew only four minutes to mix up nearly 12,000 gallons of fire retardant, and a total of 15 minutes to get it loaded onto a DC-10.

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“We strive to be quick as long as we’re safe.”

The fire retardant is colored red so firefighters can see where they’ve dropped it onto a wildfire.

Fighting a fire from the air, to help the men on the ground gain the upper hand

“The retardant really helps to buy the guys on the ground time, and to slow the flames’ spread, so that the firefighters— the wildland firefighters on the ground—can get in there and do their job.”

And what’s more is this fire retardant is designed to cling onto vegetation for years and will work to stop flames until washed away.

The retardant is also made up of a fertilizer to help vegetation grow again after a wildfire.

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In the last couple of days, more than a dozen air tankers carrying fire retardant have left McClellan to fight the Rim Fire.