This is not just to acknowledge that in 1604, all Shakespeare's characters, and those of his rivals, were played by male whites, except for the characters in elaborate masques written and staged in private palaces for the aristocracy, in which women sometimes took part. (The women were also white, of course. Ben Jonson's Masque of Blackness is an interesting example of a play written to be performed by women in blackface.) It's a given that the Elizabethan and Jacobean theatrical world was not a racially diverse milieux, although it's not impossible that of the hundred or so black Londoners of the early seventeenth century, one ortwo found their way onto the stage. When we consider Othello, a play about a Venetian general of Moorish descent, we grant that in Shakespeare's time, his part was played by the white Englishman Richard Burbage, the King's Men's chief tragic actor. But when I say Othello was scripted for a man in blackface, I don't just mean Shakespeare knew Burbage was going to play the role. I mean he wrote lines within the play that specifically refer, metatheatrically, to the fact that Othello's part is being played by a man in blackface.
Blackface was a two-century-old tradition in the English theater by the time Shakespeare came along. Readers may be dismayed but not surprised to hear that the custom was initially employed for the representation of devils in Christian morality plays. In a chapter called "Folly as Proto-Racism" in his The English Clown Tradition, Shakespeare scholar Robert Hornback describes the early English tradition of blackening stage-devils' skin in plays like the medieval Fall of Lucifer so as to present them as both demonic (smeared with soot from Hell) and foolish. Unhappily, the Renaissance stage extended the blackface-devil connection to Africans when, in its secular plays, it began to stage plays about Christians and Moors (like Shakespeare's Titus Andronicus, pictured above), using similar stage-paint techniques -- soot mixed with water or oil -- to represent the latter.
Othello is a particularly interesting play in that its dialogue acknowledges that the hero's blackness is makeup. Or, at least, it contains numerous reminders of the fact that coaldust, pitch, soot, soil, or grime discolors (colors?) white faces, which is much the same thing. Words that refer to artificially blackening agents are used throughout the play to describe various sorts of darkening. Othello says at one point that "passion" has his "best judgment collied" (darkened with coaldust). Iago claims he'll turn Desdemona's spotless virtue "into pitch." Othello calls his face "begrimed." (Imagine Burbage saying the words, or Olivier. They were literally correct.) Emilia later compares Othello's ignorance about Desdemona to "dirt."
Of course, Othello isn't the only Shakespeare play that uses many terms to describe blackness. But it's the only Shakespeare play that uses this way -- references to the ingredients of blackface stage makeup -- to describe darkness. Compare, for example, Macbeth, a play awash in references to the dark. The air in Macbeth is filled with "fog," and Lady Macbeth calls for a "blanket" of darkness to hide her murderous purposes. On a starless night, Banquo says heaven's "candles are all out." The bat is "cloistered" by the dark, and the night, hiding things from view is "seeling," which means sealing the eyelids of a falcon shut. Darkness is light that "thickens," and the wood is "rooky": filled with dark birds. Evil deeds are "secret" and "dismal" like the shadows of hell. In Macbeth, atmospheric images like fog and murk and "thick" light are the ones most often used to signify the dark moral netherworld in which the Macbeths move.
Not so with Othello. Even though, as in Macbeth, Othello's "darkness" metaphors are often employed to describe mental confusion or evil intent, those metaphors are drawn from a different source: the actor's fraudulent blackface kit.
I don't know why, in his play about a black man, Shakespeare chose to undermine the authenticity of his white actor's character by calling attention, in dialogue, to the fact that the blackness was a stage-trick. Perhaps it was a way of being more truthful by calling attention to the lie. "The truest poetry is the most feigning," says Touchstone in As You Like It. That is, art that signals its own illusions is more honest than art that presents fantasy as truth.