Oily spots appeared overnight on wall

[D__Q]

Bought an old end of terrace (1906) house about 8 months ago.

All of a sudden this morning I noticed some strange oily spots appear under the windowsill. This is an external wall and generally the room is pretty well ventilated. Gets warm in that room, at the back of the house, during the morning but cools down as the day goes on. There’s a chimney breast in that room but not on the concerned wall where the spots are. Half of the concerned wall adjoins to the bathroom and the other half is just brickwork on the other side as it’s external facing. The window is usually cracked open at all times. Was pretty hot yesterday but it was hotter for a longer period a few weeks ago so not sure it’s that

Any ideas?

Pics attached

 

[JohnD]

are you sure it is oil not water?

rub it off with a clean white tissue and see if it dries away or stays oily

does it have any odour?

knock the wall. does it seem solid, or hollow?

is there a bathroom or kitchen near these spots?

looking at the skirting, is there any chance somebody might have dropped a drink or bottle? Milk, perhaps?

 

[D__Q]

I had to go out just before noticing the blotches.

When I got back in the evening the oil/grease marks had 'soaked in' kind of and were of a darker nature with no shine.

No odour, bathroom adjoins to this wall but not where the stains are (as these are located under the windowsill, so on an external facing wall)

It's a solid wall - had guests stay in this room a week ago and it's also my office, so would have noticed if they sprayed hairspray or deodorant or something

The drip marks on the skirting have been here since I moved in

I've used some washing up liquid and the marks are mostly gone, though if you look very carefully you can see them still

 

[JohnD]

Some insects and spiders leave marks, but you seem to have a huge number.

 

[JohnD]

a diagnostic test you can do anyway:

tape a piece of clingfilm or clear plastic tightly to the wall, after cleaning. if more spots form on the room surface of the plastic, you know the source is in the room.

but if they form on the wall, behind the plastic, you know they are coming through the wall. I suppose it's possible there is something under the paint, but this usually happens on a chimneybreast, or adjacent to a shower or other source of damp.

this technique is very handy to differentiate condensation, from a wet wall.

i read book by a damp surveyor, where he found condensation caused by a cold store on the other side of a party wall; and grease penetration where the neighbour had a chip shop and years of oil vapour and splashes soaked through the brick. Both very rare and improbable causes.

put a large sheet of clean white paper or card on the floor in case there is a drip from above. Any pets in the house?

 

[Alec_t]

Has anyone been using hairspray or deodorant spray in the room?

 

[RandomGrinch]

Furniture polish when dusting the skirting?

 

[D__Q]

Possibly could have been some cosmetic product, but that was a week before the marks showed up.

I've managed to clean them off with some washing up liquid and the marks are mostly gone, though if you look very carefully you can see them still

Haven't done any polishing or spraying of anything in that room

Will keep an eye on things and see if they return

 

[freddiemercurystwin]

Furniture polish when dusting the skirting?

Keep it nice, don't judge.