Can anyone tell me what the black is under the chimney? Can I get it off?

[-CICS-]

It is not the best picture. However, I washed the roof earlier in the year and never saw the black under the chimney's. They recently called wanting to know what it is. I should probably know this by now. However, after searching I couldnt find a good answer. Thanks

 

[A to Z Roofing]

Check and see if they had a repair done, maybe someone used a product that ran off and stained the roof. Outside of that it must be either soot or algae.

 

[randyr5150]

Looks like rust from the flashing and or steel cuts into the brick, the paint may have been compromised and caused an older metal flashing to rust. Along with the use of the SH depending on whether you rinsed or not, the dwell on the flashing may have given it enough to rust and wash down the shingles. Is it black or rust colored? If it is definitely black I would say soot, but not algae. A chimney sweep or a brick contractor would be the next call. It may need tuckpointing and seeping soot out of the motor joints, does the chimney get used, did you clean in the fall and they burn in the winter, many different questions to ask.
My best guess.
Kim R.