What I found was a home in a low valley with a river nearby and road construction at the driveway. The homeowners said they powerwashed the home and this mold was not coming off. The first picture is how I found it, the second is how I left it. Because of the homes location near the river, and road construction. The exterior of the house was absorbing dirt. I used an industrial cleaner to clean the hardened dirt and caulk. Greased Lightning, Purple Stuff are fantastic industrial cleaners.