White scum on subway walls?
February 2, 2007 1:35 PM   Subscribe

What is the white scum that builds up on tunnel walls?

You can often see this from the subway--white or whiteish deposits on the walls, possibly from minerals in the water that's leaking down. Often appears vaguely bulbous and organic.

What is the name for this and what causes it?

I'm Writing A Novel that features some subway tunnel scenes, and would love to have a better way to describe this than "blubbery wall froth" or "tunnel drool".
posted by crookedneighbor to Writing & Language (5 answers total)
 
Best answer: Efflorescence.
posted by GuyZero at 1:38 PM on February 2, 2007


Best answer: Efflorescence?
posted by weapons-grade pandemonium at 1:40 PM on February 2, 2007


Response by poster: Amazing. Google image search confirms this is exactly what I was talking about.
posted by crookedneighbor at 1:43 PM on February 2, 2007


Another vote for tunnel drool.

And yes, it's mineral deposits from water leaking down and leaving deposits.
posted by defcom1 at 3:23 PM on February 2, 2007


Didn't Poe call this nitre? Techically nitre is potassium nitrate.
posted by oflinkey at 6:51 PM on February 2, 2007


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