Blackface is the act of a non-black person ‘dressing up’ as black for amusement. Its offence lies in the historical context within which it can be placed: it can be found in various colonialist relationships across the world – in America during the height of slavery, in Britain – where fair-skinned people painted their faces black as a form of entertainment, by exaggerating the aesthetics of black people.
In America, blackface originated in minstrel shows in the nineteenth century. White actors would paint their faces black using grease paint in their depictions of plantation slaves and free black people.
But these depictions often exaggerated offensive stereotypes at the time – that black people were lazy, that they were unintelligent and inferior in some way.
Within a slave, and then post-slave context, these caricatures reinforced harmful stereotypes.
It exists within a structure of power, and even today black people are disadvantaged in a variety of economic and cultural ways in parts of the western world. Wearing blackface is offensive because of this hierarchy of power.