I can remember my grandmother telling us, that to clean the copper (coal fired water heater for washing clothes etc) chimney, she used to go to the chemist and by two pennyworth of blackpowder which was wrapped up in several paperbags, they would get a good fire going under the copper, open fire box door chuck in package close door and wait for the bang. Cleaned the chimney a treat.
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Riding with enthusiasm upon the ragged precipice of disaster