The soot reference sounds vaguely familiar, in the past someone referred to it as "greasy".
The soot could have been vestige of the recausticizing process from the mill, it on occasion would put out some sort of lime byproduct into the local atmosphere. The mill would give away jugs of "vinegar" (I expect dilute acetic acid) for locals to wash their cars as this product could build up a filmy layer on the cars. I expect the intervening ten years may have washed off this residue.
The soot could have been vestige of the recausticizing process from the mill, it on occasion would put out some sort of lime byproduct into the local atmosphere. The mill would give away jugs of "vinegar" (I expect dilute acetic acid) for locals to wash their cars as this product could build up a filmy layer on the cars. I expect the intervening ten years may have washed off this residue.
