Here's What’s in California’s Huge Foam Blob

The rolling waves of waist-deep white foam filling the intersections of Santa Clara, California on Friday puzzled onlookers both online and on the street. Some thought it was sentient and others biked through it, but everyone was having a good time. The foam, flowing out of the building occupied by Signature Flight Services, a jet engine maintenance business, has been identified by officials as a type of flame retardant, according to local news outlet KTVU.

This flame retardant is similar to the stuff that squirts out of your average fire truck and isn’t all that different from the foam that’s dropped on burning forests during wildfires. Thick, foamy, and flame-resistant, the slurry of often-noxious chemicals is meant to do two things: Coat whatever is burning so that it loses contact with oxygen, thereby thwarting the combustion process, and reduce the temperature of the fire itself.

It’s not clear what specific brand of foam Signature Flight Services uses, but it’s obvious it’s of the class of products known as “high-expansion foams,” which are used to fill huge spaces — like airplane hangars or city streets — as quickly as possible.

The best type of foam for putting out flames from jet fuels is known as “AFFF” — short for “aqueous film-forming foams” — and is usually a mixture of water and surfactants, which are molecules that reduce the surface tension between liquids. We encounter surfactants every day in the form of dish soap — they’re what allow bubbles to maintain their shape. The hydrocarbon-based surfactants and fluorosurfactants in Santa Clara’s foam monster play a similar role to soap in this scenario, only on a much larger scale. The “bubbling” action of the substance, usually propelled by the contents of a massive in-hangar water tank, allows it to spread rapidly, which is crucial if the goal is to throw a huge, wet, soapy blanket on a flaming slick of jet fuel.

Fortunately, there’s no fire in Santa Clara, only an endless, undulating blob of foam, as if the building Signature Flight Services claims is their office is actually a repository for the world’s largest can of shaving cream. It’s not entirely benign, though: The chemicals in the foam are can be pretty toxic, especially if they get into the groundwater, although a moderate amount of exposure seems perfectly safe, if the above videos are any indication (the bike dude is probably going to be fine).

Good thing, then, that the state of California has past experience with giant foam attacks to draw upon. In 2008, firefighting foam filled an airplane hangar in Long Beach, expanding so quickly and rapidly it even reached the ceiling.

It’s unclear how and when the city plans to clean up the foam, but it seems a shame to let it go to waste. If you ask me, if Santa Clara doesn’t turn this into a huge block party, I officially give up on California.

Not a real llama.

Don’t worry, this didn’t really happen. The llamas are fine.