What is this black, ink-like stuff in my bathtub and what’s causing it?

March 19, 2024 3:59 PM

For the last 6 months there have been some mysterious black spots and specks that seem like some kind of ink in one of our bathtubs. I cannot for the life of me figure out what it is or where it’s coming from. Pics and video inside

https://imgur.com/a/cb0jqxu

This black stuff, which behaves kind of like ink when smudged, has been appearing in our downstairs bathroom. I have tried taking all the kids’ toys out, putting white paper inside the tub to see if it’s something from the ceiling, etc. and still can’t figure out the source. The tub and tiles around it were re-glazed over a year ago in all white - nothing seems to be flaking or peeling off so I wouldn’t think it has anything to do with that?

The black stuff will be in cups and toys, on the tub itself, and on top of and under the bath mat. I had replaced the previous mat thinking it was coming off of that but within a week or two of this new mat the black stuff started appearing again! This is driving me crazy that I can’t figure out what this is or where it’s coming from!

So hive mind - what is it??

posted by arm426 to Home & Garden (16 answers total)

Do you have a shampoo bottle losing its letters?
posted by phunniemee at 4:04 PM on March 19 [1 favorite]

This has happened to me before! But oh so long ago I've forgotten what was causing it. I believe it was a decaying rubber gasket in the faucet? How old are your faucets?
posted by AbelMelveny at 4:13 PM on March 19 [3 favorites]

I bet that's gunk that's coming from the pipes. A plastic drain augur, followed by some Drano, should get rid of your specks. Prepare to be absolutely grossed out, though!
posted by kingdead at 4:25 PM on March 19

Are you sure that’s not mold? We had the same kind of bath mat; it and the kid’s toys would get nasty despite us keeping the bathroom quite clean otherwise (for example we’d always hang the mat to dry but damp ambient air + the otherwise invisible stuff that comes off bodies when they bathe just inevitably results in gunk).
posted by lovableiago at 4:26 PM on March 19 [2 favorites]

If you have kids with bath toys that have holes in them that can get water inside they can mold inside. When the kids play with them by squeezing water in and out the mold it can come out.

Hopefully not it, but an easy thing to check.
posted by AlexiaSky at 4:40 PM on March 19 [6 favorites]

If you have an exhaust fan in that bathroom, I’d guess that’s where it’s coming from.

A la it’s on the fan blades and housing, and when it builds up enough it gets flung around especially when the fan starts and stops.
posted by jamjam at 4:48 PM on March 19

Could also be coming from the duct work behind the fan if the spring-loaded flap which is supposed to prevent back flow when the fan is not running is so gunked up it doesn’t seal properly.
posted by jamjam at 4:52 PM on March 19

Response by poster: No vent fan - and I left plain white paper in the bath for two days to see if it was coming from the ceiling or air and they were totally spotless.
posted by arm426 at 4:54 PM on March 19

This: bath toys that have holes in them that can get water inside they can mold inside. When the kids play with them by squeezing water in and out the mold it can come out happened to us. Small black flecks , sort of oily or slimy. It was seriously gross, i threw a lot of them out/replaced them.
posted by 15L06 at 5:27 PM on March 19

The bath toys can go in the washing machine for a soak and wash... I've had good luck doing runs first with dish soap, then with vinegar. I've tried bleach, too, but do that at your own risk...

(Rubber ducks and squeeze toys that spray are culprits that might result in exactly this issue... and this is how I've cleaned them and solved the problem.)
posted by stormyteal at 6:18 PM on March 19 [1 favorite]

Have you flushed your hot water tank?
posted by mono blanco at 7:04 PM on March 19 [2 favorites]

The smeary greasiness makes me think of of disintegrating rubber. Maybe check your tub stopper and any rubber parts in your tub spigot or shower head?

Some process-of-elimination troubleshooting ideas: Separately, run water into a bucket from the tub spigot, then the shower head to see if it's from one or the other. Put the kids' tub toys in a bucket with water from another source, one at a time, and agitate/squeeze vigorously to see if one of them is the source.
posted by fussbudget at 7:27 PM on March 19 [1 favorite]

In addition to disintegrating gaskets, it could also be the inner lining of a flexible supply pipe, if you have one of those. I've seen this in tubs with a handheld showerhead and in kitchen sinks with the detachable sprayer.
posted by Acari at 7:29 AM on March 20

My guess is mold. Those mats keep moisture around. With no vent fan, seems more likely that the room stays humid.

I would just keep trying to make sure everything gets dry after every use (e.g., hang the mat, dry the toys, keep the door open while not in use, use a small fan to push some air through). I'd also clean the drain, if I had not done so in a while.
posted by bruinfan at 7:33 AM on March 20

We had something like this (with the smearing), and the hot water tank was indeed failing. Good luck!
posted by chocotaco at 7:42 AM on March 20

This: bath toys that have holes in them that can get water inside they can mold inside. When the kids play with them by squeezing water in and out the mold it can come out happened to us. Small black flecks , sort of oily or slimy. It was seriously gross, i threw a lot of them out/replaced them.
This has happened to me too.
posted by dg at 6:45 PM on March 21