We have removed rust from roofs but not roof soot from fire place exhaust ports. it leaves a very black stain around the pipe on the shingles and we have tried everything to remove it with no luck. there have been over 10 houses that i can think of this year with this problem. does anyone know a product that will work for this
For the shingles I have used roof mix with double the surfactant (Green Wash of course). Apply several coats and let dwell for at least 15-20 minutes before rinsing. This has removed some soot stains completely and lightened others that were more darkly stained (repeating this process did help with the darker stains but still wasn't able to completely get rid of some).
For the brick I used a mild acid with hot water and scrubbed (alot) with a stiff bristle brush. For the mild acid I used white vinegar (I was skeptical at first but it works and I didn't have to worry about damaging the shingles with the run off). Only problem I found is that some chimney joints cant stand up to too heavy of brushing. The hotter the water.. the easier it came off.
TSP Works well. One of it's main cleaning resources is for cleaning soot. I have used it for soot quite a few times and have never had a problem. TSP is made for soot. Give it a try.