On the Padstow Museum site there is an archive page about the May Day tradition that says that in the 1840s it was customary to smear bystanders with soot or lamp black and that this may well be linked to the Darkie Day tradition:

"Origins of Darkie Days.

In the 1840's the practice of smearing bystanders with soot or lampblack formed part of the ritual along with the firing of pistols to start the proceedings.
This face blacking forms an interesting link with the "Darkie" tradition that takes place on Boxing and New Year Day.

One could say that the May Day tradition has given Padstow an advantage over many communities in that a special awareness of this unique day makes other less high profile customs no less important to keep up. This is true of the Carols sung in December and the Boxing Day and New Years Day "Darkie" celebrations.

The drums and accordions are there as on May 1st but the numbers are relatively small and the dress echoes the minstrel groups that were such a big part of the popular music culture for over a century. The music repertoire also reflects this era – fragments of once popular songs strung together performed with noisy enthusiasm. It is perhaps just as well that some of the words pass unnoticed. Where else but in Padstow would the fate of "poor old Ned" who's "gone where the good niggers go" be mourned with such feeling. Stephen Foster wrote this song and any suggestion that slaves may have sung it on the quayside of Padstow is unfortunate conjecture.

It is worth noting that the concept of "black face" had been around in Europe long before white Americans started mimicking black entertainers. Mummers and Morris Dancers blackened their faces to avoid recognition and to assume an 'other' identity. On this basis we can readily assume that the arrival of the "minstrel" idea in Padstow replaced an earlier mumming tradition that is known to exist.

It is claimed that visits to Capetown S. A. by minstrel groups inspired the formation of the 'Coon Carnival' also known as the 'Minstrel Carnival' which still takes place, post Apartheid, on New Years Day among the Cape Coloured community of that city.
Old customs of the people, performed by the people, adapting to an every changing world."

Mayday

LFF