White powder in the corner of my bedroom on walls and floor?

September 14, 2018 2:03 AM

I was about to go to bed when I happened to notice what looked like some powder in the corner on the floor. Upon closer inspection, the powder is coming from the walls. Photos after the jump.

Here are the photos: https://imgur.com/a/BHYhpCw

There was more trapped in the corner, but I took my finger and wiped it off, which was probably stupid to do since I don't know what this substance is. It was light and didn't stick to my finger. When I pulled out my camera and took photos with the flash, I noticed a lot more of that powder than is visible to my naked eye. You really can't see it in person on these white painted walls.

What is this stuff? I live in a studio apartment and I have a little "nook" for my bed. This is in a corner toward the foot of my bed and I don't see any of it in the corner at the head of my bed. There is an air conditioning unit on the center of the right wall in the photos. On the other side of the right wall is my bathroom. The left wall in the photos has another apartment on the other side. I haven't noticed any powder like this anywhere else in my apartment.

I don't know what material the walls are made of. My floors concrete. (It's an industrial-looking, hipster sort of warehouse-style place but a building that was built in the last five years.)

What is this? How can I figure it out for sure? Mold? Efflorescence? ("Efflorescence" is what comes up when I google "white powder on walls" but it seems to only occur in basements.) Something else? Should I worry about my health? Thanks in advance.

posted by AppleTurnover to Home & Garden (11 answers total)

That corner looks exactly like my skirting board between drilling a hole in the plasterboard wall and wielding the vacuum cleaner. So I'd be pretty sure I was looking at dust from the wall.

That paint job looks pretty sloppy, so it's almost certain that the plastering job behind it is crap as well. I suspect you might be looking at deteriorating gap filler, possibly helped along by a bit of efflorescence from condensation forming on a metal jointing strip behind the plasterboard in the corner or perhaps a small leak in the shower recess (the bathroom walls are probably crappy as well).

If that wall were in a house where I lived, I'd be vacuuming up the dust on the carpet, wiping down the efflorescent-looking corner of the wall with a damp rag, and keeping an eye on it.
posted by flabdablet at 3:13 AM on September 14, 2018

Response by poster: (Truly the main thing I care about is whether I should be concerned it could be bad for my health. Since I know nothing about buildings or plaster or "gap fillers" or paint and so on, if any responses could include whether or not I need to be worried from a health standpoint, I'd appreciate it! To the naked eye, I don't really see the powder and I don't even see that chips/dents in the wall that are apparent in the pictures - cosmetically it looks fine. Ok, no thread-sitting from me. Thanks!)
posted by AppleTurnover at 3:37 AM on September 14, 2018

Efflorescence can occur anywhere where brick gets damp. It can be due to damp rising through porous brick from the ground, or water ingress from the outside (e.g. a drainpipe or gutter failing, allowing water to run down the wall outside). Normally you'd see an issue above where you find the powder - flaking or bubbling paint or plaster.

If there's no other sign of damp, it could just be an issue with a new plaster wall that was painted with a water-based paint without being allowed to fully dry out - this can led to the paint turning powdery.

Anyway, I'd just clean it up and check again in a few weeks. There's no health risk from a bit of plaster/filler/paint dust; my family would all be long dead if there were, the amount of the stuff I kick up in the average year with my DIY-ing...
posted by pipeski at 3:55 AM on September 14, 2018 [5 favorites]

The dust looks very much like dust when you drill or cut drywall, which is almost certainly what your walls are made of. I assume it's same because it's used everywhere.

Vacuum it up and don't worry about it.

I would be curious as to why it showed up suddenly. They don't spontaneously generate dust AFAIK. It might be dust from prior work that got shook by something. For instance, pounding in a nail to hang a picture might shake out dust. Maybe the nook was built recently and someone in a neighboring apartment gave the building a good shake.
posted by Awfki at 3:56 AM on September 14, 2018 [4 favorites]

Looks like paint dust to me. Maybe the AC unit is shaking the walls a bit when it turns on? The only potential concern would be lead, but lead-based paint has been illegal since the late 70s, so you're ok there.
posted by basalganglia at 5:56 AM on September 14, 2018

I know nothing about buildings or plaster or "gap fillers" or paint and so on

Plaster is mostly calcium sulphate and calcium carbonate. Both are fairly body-friendly substances unless you huff enormous quantities of them in powder form and clog up your lungs. Skin contact or ingestion of small quantities will do you no harm at all. So if there's plaster dust in your environment, the best thing you can do for your health is vacuum and/or wipe it up.
posted by flabdablet at 6:45 AM on September 14, 2018 [1 favorite]

Clean it up with a vacuum and dusting cloth -- and see if it comes back. Also take a paperclip and poke/probe the wall where you see dust, and nearby where there's no dust. Is there any weakness there?

If so there's probably a moisture problem in that corner. Has the weather been particularly damp?
posted by seanmpuckett at 7:39 AM on September 14, 2018

How old is the building? If you're worried about the possibility of lead you can get a lead testing kit at a hardware store. If the building was built after 1978 it's unlikely to be a problem.
posted by under_petticoat_rule at 8:27 AM on September 14, 2018

That's efflorescence. Not harmful. Clean it up.
posted by humboldt32 at 9:03 AM on September 14, 2018

Response by poster: Thanks all. I don't know why that corner would be damp and not the other corner in this nook. I do notice that this wall under the air conditioner unit, if I catch the light at the right angle, I can see what look like drip marks all down the wall. I have to try hard to see them as they are very faint, and I've never actually seen any water or moisture coming from the air conditioner, but that is there. I will wipe down the wall and try to erase those and see if they come back too. The other side of this wall is the bathroom and I do take long hot showers, I guess. I'll clean up with powder and monitor it.

Anyway, I'm glad to know this doesn't seem to be mold or something that could affect my health. I'm curious why no thinks it is mold? I guess because of the pattern it appears and the fact that it clearly has fallen onto my floor like a powder? Anyway, thanks.
posted by AppleTurnover at 11:30 AM on September 14, 2018

I'm curious why no thinks it is mold?

Because if it were mold, you'd see dark patches appearing on the walls well before you started seeing loose spores of any colour.
posted by flabdablet at 11:32 AM on September 14, 2018 [1 favorite]