Gross ‘black slime’ creeps over Washington DC’s most famous monuments


  • Black slime, otherwise known as biofilm, has been creeping over the National Mall monuments and other iconic areas for a decade
  • The biofilm really only needs nutrients and a surface to grow 
  • The National Parks Service has hired scientists from all over the world to find a solution 

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16 Comments on Gross ‘black slime’ creeps over Washington DC’s most famous monuments

  1. It’s black, it’s alive, does it matter? Barry and Hillary are the slimy part.

    Flamethrowers, I suggest.

  2. When you’re done cleaning the monuments, be sure to get that slime out of the White House.

    The comments write themselves.

  3. Hired scientists from all over the world?! At what cost?

    I just purged my hot tub plumbing of biofilm at the beginning of summer. It was a product called Ah-Some and it sells for about $20/2 ounces. Lasts a long time and breaks down the outer layer (film) that the microbes ‘build’ to protect themselves. Whoosh! No more biofilm. If you have a jetted tub or hot tub, use it. Otherwise, you are bathing in a sea of ewwwuuuu every time you slip in for a bit of relaxation.

    Nothing else works.

  4. AA – different critter. Down south that black stuff is everywhere. Roofs, driveways, brickwork, etc. Any good ol’ boy knows to break out the pressure washer. It’s tenacious, but comes off with that. Problem is that after years of annual pressure washing, even concrete slightly erodes as will the marble. I’d love some brush on, hose off stuff but I don’t know that there is such a thing that won’t also kill my grass. A better mousetrap waiting to be built, but scientists from around the world? Cue the toilet flushing sound FX. “$50 million Nat’l Park Service study concludes pressure washer needed to get black crap off monuments. New study commissioned to prevent erosion from washing.”

    The view from 30k ft has us exercising a lot of hubris to think we are excepted from paying the wages of time. Go to any cemetery with 100yr+ tombstones to see the future of any monument. We can delay, clean, maintain, etc, and I’m not saying not to, but we’ll get there. Kind of like my greying hair. The clock ticks relentlessly on. Revere and respect what they’re there for. Don’t lament that they don’t look brand new.

  5. Black, Brown and White slime thrives in Washington DC, NYC, Detroit, Chicago Dearbornistan, East St. Louis, Memphis, Atlanta, Ferguson, LA, and all major metropolitan inner cities controlled by democrats for the last 50+ years.

  6. @Gojira — Oh, now I know what you’re talking about. I was mislead by the term ‘biofilm.’ It sounds like they are misusing a term, then, in order to make it sound more mysterious, a cure more elusive (and costly). So like our illustrious spenders in D.C., huh?

    So funny. I researched this exact problem to find a solution for the same black crud problem on our church in Seattle; a 100 year-old stucco and cast stone building on the historic register. We can’t do a thing to it without jumping through a bazillion hoops to make sure we aren’t ‘degrading’ its historical-ness. It’s a real pain. But the cast stone ornaments (rope details, animal figures, etc) are very fragile and once they’re lost, they’re lost.

    I did find a national company whose specialty stone cleaning products are used on brick, stone of all kinds, etc. It’s bloody expensive to use, but they work. The EPA requires a used water recovery system be set up on the perimeter of the building and you almost have to have special training (like asbestos abatement) to carry out the work. It’s stupid, because the stuff isn’t ‘hot.’ Apparently the company doesn’t have a big enough lobby in D.C. lol!

    You can see, for example, picture of before and after they cleaned St. Patrick’s Cathedral in NY, on the internets. I can’t remember the name of the mfg.

  7. @Abs – that term, biofilm, is one that has been cropping up in a clinical setting for 10-20 years now when they discovered that small caliber pipes/tubes in medical and dental devices invariably build up a polysaccharide matrix with all manner of bacteria living in it. Huge eww factor so they have been treating it. I think your hot tub cleaner mfr hopped on the bandwagon because it sounds so, ya know, all scientific n’ stuff to lay people.

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