Our kitchen has one of the main walls of our house which is a thick concrete wall. There is nothing behind the wall, just some empty space and then the neighbor's house. I just painted the wall with Flexa indoor water-based color, as grey.
Now, as you can see in the pictures, after a couple of months we see some green spots on the wall in different places.
My question is, what are these green spots? They don't look like mold or mildew.
Update
- I just tested our cleaning sprays on the wall to see if it happens because of some spray drops but it was not the case.
- This place is not reachable for our kids.
Best Answer
Looks like copper corrosion products - so if there is a bit of copper embedded inthe wall, this sort of staining to the surface is quite plausible. WHY there's copper there to cause staining, I can't tell you.