(nyt) SILKY straight hair has long been considered by many black women to be their crowning glory. So what if getting that look meant enduring the itchy burning that’s a hallmark of many chemical straighteners. Or a pricey dependence on “creamy crack,” as relaxers are sometimes jokingly called. Getting “good hair” often means transforming one’s tightly coiled roots; but it is also more freighted, for many African-American women and some men, than simply a choice about grooming. Straightening hair has been perceived as a way to be more acceptableto certain relatives, as well as to the white establishment. “If your hair is relaxed, white people are relaxed,” the comedian Paul Mooney, sporting an Afro, says in the documentary “Good Hair,” which won a jury prize at the Sundance film festival and comes out in October. “If your hair is nappy, they’re not happy.”