Had a 70 year old retired sweep school me on soot analysis last week

I was telling him about a job I did in a 1920s house with all this weird greasy soot and he just laughed and said 'that's not creosote, kid, that's old coal residue mixing with furnace oil.' He spent 20 minutes explaining how different fuel types leave totally different residue patterns. Has anyone else had an old timer drop knowledge that totally changed how you look at a dirty chimney?

2 comments

2 Comments

richardharris1mo ago

That "weird greasy soot" thing is actually a pretty good clue, but it's more likely from years of burning green wood than old coal mixing with furnace oil. Coal residue is usually more dry and powdery, not greasy.

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maxp681mo ago

Notice how people always jump to the fanciest explanation for things when the boring one is usually right. I mean, I see it all the time with old houses - someone finds weird paint and thinks it's lead-based when it's just cheap latex from the 80s. Green wood smoke makes everything greasy and tar-like, especially in a chimney that's seen a few decades of use. Maybe it's just me but the simplest answer is usually the one that matches what you actually see in real life.