Wednesday, January 28, 2015

Out, damned spot!

OK all you millions of  hundreds of  four readers out there, I need your help.  On Eolian's decks hundreds of black spots are slowly appearing, and have been ever since we repainted the decks.  They don't grow fast, but they do grow.  Nothing seems to touch them - using straight bleach has no more effect than plain water.

My questions to you are these:
  • What is this stuff?  Is it a lichen of some kind?
  • Does anyone have any experience with it, or are we the only ones? 
  • Most importantly, how do we get rid of it?



Dave said...

Do they scrub or smear?
I'm guessing something in the paint.
Try leaving a small rag soaked in vinegar laying on a patch of them for the day. Keep it wet, with Vinegar, placing a bag over it if need be. The mild acid will react with the spots if they are iron contaminants.
Best of luck,
Dave, SV Ava Chantel

Robert Salnick said...

Thanks Dave - I'll give the vinegar a try!


Steve Stark said...

Sharply defined edges following the paint grain boundaries. Suspicious... seems to be inorganic.

Time for a scraping and a trip to the mass spectrometer - maybe at a UW lab?

s/v Starbright

Robert Salnick said...

Thanks Steve - I'll see whether I can find access to one...


SV Pelagia said...

OK, this response is not going to give you the solution to the spots, but hopefully will allay fears of permanent staining.

I recall last Summer a friend's boat in Vancouver having EXACTLY the same black spots... MANY black spots. He was working on removing them.

Sorry I cannot remember his solution (and we are not in Vancouver at the moment), but he said it was terribly difficult and he was successful in removing them. That should alleviate some concern and keep you searching.

SV Pelagia

Anonymous said...

Don't you have an oil refinery up wind of you?

Robert Salnick said...

Thanks David, for the hope!


Robert Salnick said...

Anon -

Indeed. But really, it is more "side wind". And these are not spots of petroleum/bitumen/asphalt. They grow. And they started appearing in Seattle, years before we moved to Anacortes.


Mitch Brown said...

Have you tried a small 1500-1800 ps electric pressure yet. work wonders on my deck

Robert Salnick said...

Mitch -

Eolian's non-skid is paint with sand in it - I worry that anything strong enough to wrest away these spots (they are tenacious!) could damage the paint. But eventually it may be worth a try as a last resort...


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