Cleaning the black sluge from radiators off of walls

[Kitsune]

Not sure this is the right place for this but thought plumbers might come across this issue. We have had our whole central heating replaced (one pipe system) and in the process some of the black sludge from the old pipes has been splattered on the walls.

Any ideas on the best way to clean this without leaving marks or damaging the paint (Dulux matt), I tried in a small corner and leaves a grey mark, the room is fairly recently decorated so don't fancy doing it again.

Cheers

 

[Newboy]

Regrettably there's no way to remove the sludge residue. Wipe down and repaint.

 

[Kitsune]

thought that might be the case, at least only one room has been decorated