This is found in a basement ceiling from 1908. I don’t think the white is from paint because only the area with the white and black has the white. My only thought was from a slow leak from a radiator. Any other ideas? …:roll:
Sure looks like a prior water leak but a quick test with a moisture meter should confirm it. As to what is the white substance, depending on your location it might be from age or minerals or a white wash that was applied containing some type of insect repellent. You need to update your profile to include your location.
It’s probably Kilz, or other type of paint, an attempt to cover previous water damage.
A moisture meter won’t pick up dampness it’s from a leak that happened 10 years ago and has since been fixed. The stain always bleeds back through the paint.
You can tell that from one photo? Damn, you’re good!!! :razz:
Paint over fire damage, with a leak as well?
It may be white wash (not paint), it will stain like that when it gets wet.
Whoops! I left out the IF
Such an important, large, two letter word…
Not even grammar check woulda helped that one.
Good catch! 
Any GOOD inspector with the powers of observation and an eye for detail should have caught that! 
Thank you gentleman. Paul from DC area
Especially me, the “Grammar Nazi”.
That kinda crap drives me insane, and now I’m guilty :twisted: :twisted:
New day, another schoolin’! Awesome!!! :mrgreen:
OUCH!! :twisted: