Gutters can become stained with unsightly dark lines, which can be difficult to remove. These marks, called "tiger stripes," are caused by a variety of reasons. Roofing tar and asphalt can leach down on the gutter, while dirt, mold and pollutants can become electrostatically bonded to the gutter's paint. Removal requires the right chemicals and a bit of work.
Gutter cleaning requires working from a ladder, so be careful of the ladder's footing, and how much weight is placed on the gutter. A stabilizer bar is a good choice because it will keep the ladder's weight on the roof or wall and off the gutter. Be careful of electrical lines and trees. Wet any underlying vegetation, concrete or decks as well as the walls beneath the work area. This will prevent staining and plant damage.
Gutters come in several types, including vinyl, aluminum and painted surfaces. Vinyl and painted gutters are harder to clean, while painted ones need careful attention to avoid removing the paint. Make sure the cleaner you choose is recommended for your gutter type. If painted gutters show wear or bare metal, repaint and allow to dry before cleaning.
F-13 Gutter Grenade is a multipurpose gutter cleaner that's safe for all types of gutters. It attacks the oxidation and not the paint or material. For aluminum, try Gutter Zap, which removes electrostatic bonded streaks with little scrubbing. Simple Green makes a concentrated environmentally safe cleaner with good stain removing properties. Be sure to follow the manufacturer's instructions and recommendations for any cleaner.
Wet the gutter with a garden hose after pre-wetting the area. Apply the chemical according to the manufacturer's instructions. Brush the gutter with a stiff bristle brush. On stubborn streaks, let the chemical dwell longer, being careful not to let it dry. Rinse with water, and if necessary reapply the chemical to remaining stains and brush again. Be sure to rinse all plants and grass, the house walls and siding, and all decks or walks of any chemical too.
Never let your chemical dry on the gutter. If it does, re-wet and brush again to prevent leaving brush marks. Always test a small inconspicuous spot with the chemical before starting to ensure desired results. Sensitive plants beneath the gutters can be covered with plastic sheeting after wetting to protect from the chemicals.