ᐅ Dark Stains on Door Frame – Possible Causes

Hello,

Recently, the spots/discolorations shown in the photos have appeared. None of the apartment’s residents can understand how these might have formed. It is also completely unknown when or over what period they appeared.
My question is whether this might be a known issue or if anyone can provide a useful tip about the cause based on the pictures.
Brief description: Dark discolorations at the lower edge of the door frame; it does not seem to be paint and cannot be removed by wiping or scraping. It appears to be somehow "in" the wood (veneer).
Attached are two photos of the affected area, one with flash and one without.

Best regards,
N

We have similar stains in our rental apartment that supposedly appeared during the installation of the door frames due to adhesive/foam. They can no longer be removed.

Were the doors recently installed?

Grobmutant schrieb:

Have the doors been reinstalled?

They don’t look new.
Can this be wiped off?

Nanopixel schrieb:

No resident of the apartment can figure out how these could have occurred.

Who says so? Even housemates deny it.

Maybe someone used a cleaning agent that was too strong...?

No, the doors are not new. They are about 10 years old. You can’t just wipe it off (otherwise, there wouldn’t be a problem). Interesting ideas, especially regarding the strong cleaning agent. Could moisture rising from below also be a possibility, causing the stain to develop very slowly over a long period?

I can’t imagine that. Moisture tends to spread evenly, so you would expect to see something like a semicircle there. In the pictures, however, it looks more like a long streak.