"Black Folk Art in America: 1930-1980," the largest show of black folk art ever assembled -- more than 400 pieces by 20 artists -- opens this Friday in the Corcoran's refurbished galleries.

Some pieces possess amazing grace and vision, like William Edmondson's primitive stone sculptures of schoolteachers, angels "folk art." Formal artistic training doesn't get in the way of these artist/barbers, artist/preachers and fellow travelers.

The show is undeniably big, but it would have been better under a more rigorous selection process.

Aside from the pieces with witchcraft and voodoo themes, few are specifically black. Some offer religious testimony: 28 pieces of James Hampton's glittering "The Throne of the Third Heaven of the Nation's Millenium General Assembly" have been relocated from the Museum of American Art for the exhibition, backed by a brick wall to simulate the garage in which Hampton built the found-object-and-foil throne. Apocalyptic scenes on fans, windowshades and paper by Sister Gertrude Morgan, a painter, preacher and singer, include a repeated chant: "Jesus Is My Airplane." Self-portraits show black Sister Gertrude with a white Jesus as her groom.

Nellie Mae Rowe's drawings in crayon or felt-tip pen use sophisticated colors and shapes. Rowe's painted head, sculpted from chewing gum and decorated with costume jewelry, is eerie; a doll dressed in orange with glasses and wig, seated in a mini-lawn chair, titled "Self-Portrait as a Child," is perfectly bizarre. David Butler came to create late in life after a disabling accident, producing some of the liveliest "roadside" art in the show, colorful metal cut-outs of fanciful animals and contraptions.

Mose Tolliver's lyrical visions of birds, flowers and women are sometimes nightmarish. Bill Traylor, who started to draw at age 85, turned out primitive but lovely realistic and fantastical animal and human characters during a four-year art career.

BLACK FOLK ART IN AMERICA: 1930-1980 -- At the Corcoran, through March 28.