Can anyone identify the problem on some of the cinder blocks at the base
of the outside wall of my garage? I'm wondering what the black stuff is.
It doesn't rub off, and it's unaffected by bleach. Photos appear on
alt.test at time 5:49 pm, 3/17/08.
If you have the capability to search by message ID, here's the message ID
of the OP's post to alt.test.
To me, looks like used motor oil or grease oozing out of porous concrete
block. It appears to be on a flat surface that is horizontal at the base
of a well shaded and perhaps covered by a carport exterior wall.
Of course, not being there to smell or touch or otherwise examine it
closely puts one at a disadvantage.
Due to spam, I\'m now filtering all Google Groups posters.
If it's as hard as a rock, so hard a steel-bristle brush has little
effect, rub it with a vitamin C tablet. If that has an effect, it's
black algae, and a swimming pool supply will have remover/s.
The black spots are as hard as a rock, but the only effect the vitamin C
tablet had was to whiten the black, like rubbing ordinary chalk on a
sidewalk. I also dampened the vitamin C with water; no effect.
Thanks for the suggestion.
I've reposted the photos at alt.binaries.test, hoping that those who
couldn't view the original posts will have better luck. Sometimes I just
see the top photo; if I go to another message and then return to my
message, both photos usually appear.
Subject: Black foundation.
Time stamp 10:00 a.m. (Eastern Time), 3/18/08.
Sender: Ray K
One of the long garage walls is common with the kitchen; the innermost
wall across the width of the two-car garage is common with the laundry
room. The floor of the house is 8 inches higher that the garage floor.
There has never been water seepage into the garage for the eight years
I've lived here, even though some of the mortar appears crumbly after 39
The black is not tar or grease/oil, and as I originally stated, bleach
does not affect it, so it's probably not mold. The corners where the
black is darkest had been covered over with blobs of cement. When I
chiseled away the excess cement - to make it look nicer - the black
showed up, although there is also black at the opposite corner (where
the foundation meets the cinder block that supports the outside wall).
It could just be minerals in the foundation, as someone suggested. Soon
I will be painting it, but I don't want to just cover up what may be a
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.