Visiting any older city in Europe that hasn't had a good cleaning done to every building, you can really see the soot buildup that remains even today on buildin

Visiting any older city in Europe that hasn't had a good cleaning done to every building, you can really see the soot buildup that remains even today on buildings that are being cleaned[1][2] for example. Granted that was acquired over centuries of burning coal and wood to heat houses. [1]: https://www.manchestereveningnews.co.uk/news/nostalgia/manchesters-dark-history-archive-pictures-8722223 https://www.manchestereveningnews.co.uk/news/nostalgia/manch... [2]: https://old.reddit.com/r/powerwashingporn/comments/6d3l6p/this_is_the_palace_in_vienna_austria_its_in_the/ https://old.reddit.com/r/powerwashingporn/comments/6d3l6p/th...