Before revision: Black sugar was often found on porches and the cold ductwork and caused the high carbon, soot-loaded gas to precipitate on the floors and walls and crystallize.
After revision: Black sugar was often found on porches and the cold ductwork and caused the high carbon, soot-loaded gas to precipitateNewspaper Article, "Area firms working to clean up environment", Beaver County(PA) Times, Nov 20,1973, Page A-6 on the floors and walls and crystallize.