16 thoughts on “Power washing in Manhattan: Before and after”

  1. Anyone know how long it takes to get a build-up like that? Also other than soot from cars, what is making it so black?

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  2. Accurate image, misleading description. That’s pretty obviously smoke damage they’re spraying off, not an accumulation of dirt.

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    • Not necessarily…they cleaned up two buildings on Cleveland’s Public Square several years ago (Old Stone Church, and the Soldiers and Sailors Monument–both well over a 100 yrs old). No one alive had ever seen them as anything other than black stone. But after they were cleaned up, the colors of the native light gray and light brown sandstone were exposed. Over a century of industrial grime and smoke and soot, pollution from coal & oil heating, auto exhaust, and weathering had turned them pure black.

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  3. I guess if it hasn’t been cleaned since the industrial revolution, that could be from coal smoke stacks and coal furnaces. Still, it is pretty black.

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  4. Hey, my dad has a Karcher water blaster that he uses to clean our driveway of the green moss that keeps growing. He also uses it to wash the cars; pretty good stuff.

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