DownEastPowerWash
New member
Here is the deal, quite a large building which is all painted metal. It has black streaks like gutters but does not clean like a gutter. Here is what has been tried, Emulsifier plus with 12.5% bleach (no success), Mr. Muscle truck soap (limited success), WAB Squeaky Clean ds and straight (no success), two step acid wash (best results but not satisfied). All detergents were used in various strengths brushing and no brushing. Even tried GutterZap which works great on gutters but nothing on these streaks. I tried heat and not heat as well. Really don't want to have to brush the whole building due to the size of the building. Below are a couple of pictures of the streaks. Let me know what you think and thank you in advance.