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Dead leaves, particularly those from certain tree species such as oak and maple, are known to contain various organic acids including tannic acid. Tannic acid has a pH ranging from 4 to 7. When leaves decompose on painted surfaces, these acids can penetrate the paint and may lead to discoloration or staining. The acidity of these leaves, when combined with moisture from dew or rain, can create an environment conducive to staining, especially on lighter colored paints where the contrast can be stark.

Removing these stains typically requires a multi-step approach. A solution of trisodium phosphate (TSP) at a concentration of 1-2 ounces per gallon of water is often recommended to tackle such stains, as it effectively neutralizes the acid. For more stubborn marks, a mixture consisting of hydrogen peroxide (3% concentration) and baking soda may be applied; however, testing on a small, inconspicuous area first is vital to avoid potential damage to the finish. Additionally, pressure washing at a PSI of around 2000 can assist in removing built-up organic matter before applying chemical solutions. Sealing the paint with a protective layer post-cleaning can prevent future stains, keeping the surface maintained longer.