Dirt, pollen, and pollutants are attracted to the droplets of dew that form on the lip of rain gutters. When the droplets are big enough they roll over the front of the gutter in streams. These streams deposit the grime and form streaks on your gutters better known as Tiger Striping.
Tiger Striping is a natural process that can happen to a variety of surfaces such as rain gutters, cars, metal roofs, and even the siding of your home. It is not a failure of the paint or gutter system.
Metal surfaces with baked on paint require cleaning from time to time, and your gutters are no exception. Generally, you should clean your rain gutters at least once a year. This may vary based on where you live and you may have to clean them more often, especially if you live in an area with high humidity or industrial activity..
To clean, use a soft rag, sponge, or brush to gently rub the surface. Do not scrub too vigorously, as this can lead to glossy areas over the gutter’s satin finish.
Important: do not use a cleaner with abrasive particles, ammonia, solvents or paint thinners as these can damage the paint finish. Several gutter cleaners are available on the market, but any nonabrasive household detergent will do.
It is easier to prevent Tiger Striping than it is to get rid of it, but it can be done.
Tough deposits may not come out during the first cleaning, so you may need to wash more frequently until they’re gone.
In some climates, gutters may suffer from mold or mildew. In this case the troubled area should be cleaned with the following solution: