Wipe the wall then dry it to test for colorfastness.
Yellow tar streaks on bathroom walls.
We just noticed yesterday this scenario on our hallway walls outside the bathroom.
Only thing we have done is put a metal roof on the house approximately one year ago.
Yellow sap like substance on inside walls over the last month or so we have had random spots of sticky yellow sap on our walls in weird spots.
This is an interesting thread.
The smoke and tar from cigarettes builds up on the walls and ceiling over time and eventually leads to a nasty residue that is difficult impossible to get fully cleaned off the paint.
Nicotine damage occurs simply from someone using the bathroom or an adjacent room as a smoking area.
After cleaning use the second sponge to rinse the walls with clean water.
Mineral deposits remain on the wall and build up over time without proper cleaning maintenance.
Start at the bottom and work your way up to prevent additional streaks drips from appearing.
When condensation from a hot shower or bath forms on the walls and begins streaking or dripping down the wall drip marks occur.
It means that your walls are painted with an oil based paint and its the oil coming from the paint u need to redo the walls with a non oil base paint and a mildew resistant paint made especially for bathrooms that is why u get the yellowish brown spots its the oil in the paint coming thru.
Cigarette smoke of those two potential cases cigarette smoke is usually the most common culprit.
Use one of the sponges to wipe the walls with the solution.
It is not happening in the bathroom and the hallway was painted approximately 2 years ago.
Those spots and streaks are the tar buildup from cigarette smoke and it gets so thick that it starts streaking down the walls.
These lines result after the water evaporates.
Drip marks on your bathroom walls occur due to condensation of hot shower or bath forms that started to streak down turning into lines on the walls right after the water evaporates.
For the sake of my sanity in shared shower situations i ve chosen to go with explanation 1.