The solution is contained and controlled to protect the homeowner's property at all time during the process. This is done with collection bags at the downspouts, fine control nozzles and a ground man watering or flushing any majorly contaminated areas. We do not pressure wash the roof or use a pressure washer for any part of the roof cleaning process. All black streaks (algae) will be invisible at the time we leave. Any moss may be left behind will be dead and will fall off after a few heavy rains. If you have moss or lichen and want it removed we can scrape it off, but it is not recommended as it pulls granules off the shingles with the roots. We recommend that moss and lichen be left to break at the root level after it is treated.