Hi Guys,
A client called me as they have had a new boliler installed and the wall that the vent comes from has been covered in a "soot like" substance fromn the oil burner boiler - I did a test with a mild detergent and with a good amount of scrubbing was coming off, but this is quite a large area, any other tips, for a quicker more effective clean, the wall is a yellow stippled render (not painted) and they do not want this damaged unneccesarily.
Any help much appreciated!