I think face-blacking was mainly done in the winter, and usually by mummers rather than dancers. (the Not-for-Jo morris of the Borders was traditionally done at mid-winter, I believe).

Black was not the only colour used - in sheep-farming areas they often used raddle, so faces were red or blue. But for most people soot was easily available and free, and the fact that it was black was not important.

The Cotswold Morris sides danced in Spring/Summer, and wore white, and didn't disguise themselves, as they didn't want to get soot all over their virginal costumes.

Wassail! V