The Roof Cleaning Institute Of America Training & Certification Forum
"Find A Certified Roof Cleaner Directory"

I can't remember if I cleaned under the skylight. I don't see why I wouldn't it was a 2ft area under the light. It wasn't like I was gonna waste the solution.
Good info Gary thanks.

It could be the deteriorating powder coat that most are painted with (usually a bronzetone)or the actual metal frame staining due to corrosion or even the sealant they used when installing it.

I'd take Garys advice and try a second hit after the first application had some time kill the GM (if that is what it is) and the cells had time to decintergrate

Here are the before and after pics, I had the homeowner send me the second pic so the quality isn't as good, but you can see what I'm talking about. I'm gonna give it a second shot, but that is very disheartening you tell a HO you can clean their roof, but they still got black areas on it.

Yeah Zach it sucks, I remember my first " skylight experiance " after cleaning two homes right next to each other. It was in a development so both homes had skylights same spot and same stain. I hit it with full strength and it didn't do squat, I got answers from people in that type of work right along the lines of what maverick stated above. The only thing that made it easier for me collecting money was that I could point to the house next door, they were pretty cool about it because the overall appearance of the roof was greatly improved just like your customers roof! The after photo is tuff to tell but it looks like it, I remember I thought it was just still wet. This is a valuable " situation " you had early, remember it. Look for any discoloration under that skylight on the estimate and point it out. Also look at homes that have skylights but the roof is clean, you will see that problem on some and you will develop a good eye for spotting it. I hope it's not the problem, don't get discouraged you are not at fault. Oh and while we are at it keep your eye out for " soot stains "

I dont know what brand causes the stain but I notice it on homes built twenty years ago to now. It can be alot of things that cause it, maybe over all cheap material, sloppy installation and so on. The good news is they are far and few between but when you see a roof with a skylight,chimney and wood stove pipe you got to be on the ball. I know when I get to a job and see them I say Shit! and pay alot of attention.