A few people already know that Madame C.J. (Mrs. Charles) Walker invented the "hot comb." But a new film about this queen of black beauty culture documents, for the first time, the extent to which she revolutionized the personal habits and appearances of millions of black people.

Produced by independent New York filmmaker Stanley Nelson, the film, called "Two Dollars and a Dream," also paints a compelling picture of one of the first self-made female millionaires in American history, as well as of her fabulous daughter, A'Lelia, who, at age 37, inherited the $2 million Walker fortune.

Because Nelson is the grandson of a former Walker company general manager and the son of its current president, one might expect the film to be a bit on the soft side, say as a favor to Mom.

But Nelson has used his unrestricted access to thousands of photographs and documents in a highly professional manner, so what emerges is a credible look at a continuing social phenomenon.

With Helen Humes' 1923 song, "Nappy Head Blues," as its theme, the film describes what was essentially a movement by Afro-American women in a Western culture to come to grips with one of their most unique features: hair.

At the turn of the century, nappy heads had come to connote a general unruliness in black people. Indeed, a pending racial discrimination suit by Cheryl Tatum, who says she was dismissed from her job at a Hyatt Hotel in Crystal City because she wore her hair braided, indicates that hairstyles worn by blacks remain as politically hot today as they were back then.

Say what you will, then, about the notion of "straight hair being good hair." But don't attribute it to Madame Walker. She was just minding her own business as a laundress with a knack for using the flat iron when women began asking if she could also iron out the kinks in their hair.

So many women had become tired of combing out chunks of their tightly coiled hair that they were resorting to desperate, and dangerous, remedies. In 1900, Madame Walker had a dream.

"She cooked up this secret formula right on her kitchen stove," recalled one of the elderly black women who worked in a Walker salon. "Then she came up with this idea for a hot comb. It was a miracle."

Some still criticize this rejection of "natural" hair as submission to a white standard of beauty. But one of Madame Walker's staunchest supporters was Marcus Garvey, the father of Pan-Africanism, who was more impressed by the fact that Walker employed 3,000 black people.

Besides, as Walkers' former employes note, it was ridiculous to say that a black woman used a hot comb to "look white." There are, after all, other characteristics to take into account.

But was there something wrong with black people's hair?

One former employe pulls no punches when she says during an interview, "You can't imagine how unruly it could be."

Other employes note that many white women flocked to the Walker salons because the appeal was not just to have straight hair, but to have hair styled -- something that black women had been doing for centuries in ancient Africa.

Moreover, they note, the internationally famous "Walker System of Beauty" for women was based on black pride and sisterhood, emphasizing cleanliness and health care as a means of improving self-image and asserting independence from domestic work as well as men.

With the help of preachers who extolled the Walker system from the pulpit as the beginning of a new era of "black queens and goddesses," Walker got rich. At a time when the average black worker earned $12 a week, she was making $1,000 a day, and this before there was such a thing as taxes.

The 50-minute documentary is clearly worth seeing, but because it is about a black woman whom few people have heard of, Nelson must distribute it himself.

Schools, libraries and public television stations interested in showing it should write him at 324 Convent Ave., New York, N.Y. 10031.