SIX BLACK GIANTS" is the opening show at Gallery 1221, an establishment devoted to showing and selling "investment art" by accomplished black artists who have been "Traditionally excluded from commercial galleries."

The show includes 2 dozen works, most of them small, by six artists of high accomplishment who have had varying degrees of recognition. Color painter Alma Thomas, recently honored with a posthumous retrospective at the National Museum of American Art, is the star here, even though she is represented by only a few small paintings on paper. James L. Wells, the beloved, now retired, founder of the print department at Howard University, has made a poster commemorating the opening, and some of his recent linocuts are also on view. Lois Mailou Jones Pierre-Noel, another well-known Washington artist and educator, is showing several watercolors of Haiti and Nigeria.

New York artist-illustrator Ernest Crichlow, who like many of these artists, worked with the Works Progress Administration during the '30s, is introduced with a 1967 painting titled "White Fence," which symbolically depicts the black child as an outsider in a white world. The late Norman Lewis, who taught at the Art Students League in New York, is most effective in an abstract lithograph titled "Togetherness."

But the big surprise of this show is painter Charles Sebree, 67, who has quietly lived, worked and supported himself by his art in Washington since 1965 without ever showing in a commercial gallery here. He hasn't had to, he explains, because he has a stable of regular collectors, though he has been invited to show at Henri Gallery. In his small casein paintings on textured paper, Sebree reveals himself to be a gifted artist who somehow manages to cross Picasso with Paul Klee, but, in the end, produces intriguing little abstractions that are all his own.

The gallery, owned by Washington attorney James R. Haynes, is not the first in this city to attempt to pull back the curtain that still obscures some black artists: Barnett-Aden had a similar, if broader goal, and so has Smith-Mason Gallery on Thomas Circle. Nyangoma's Gallery on 18th Street NW is a more recent entry, though its efforts extend beyond black art. What is unique -- and somewhat disturbing -- about Gallery 1221 is its emphasis on art as investment vehicle. In the catalog, for instance, one biography ends with the following: "The works of this artist represent an excellent investment opportunity for near-term appreciation on the order of roughly 15-25 percent per annum."

The show will continue through March 15, and is open Tuesdays and Thursdays from 12:30 to 6:30; Saturdays from noon until 5; Sundays from 1 until 5. Gallery 1221 is located at 1221 11th St. NW.

Valentines

Anyone hunting a Valentine for a print lover should visit Printmakers Inc., the airy atelier at the Torpedo Factory in Alexandria, where nine artists make prints of consistently high quality that sell for astonishingly low prices. June Hoke, the featured artist this month, is showing joyfully colored etchings made from metal plates that have been cut into parts (hearts, sailboats, houses and half-moons), and then reassembled and printed in various combinations. The tiny "I do I do," for example, would make an endearing Valentine ($25), with its yellow moon and red heart romantically afloat over a cozy old house. "Dream Boat" is the most successful of several larger monotypes that incorporate etched segments. The show continues through February, and is open every day, 1 to 5.

Print Sale

On the subject of prints, Jane Haslem, 2121 P St. NW, is holding her annual print sale this week, through Saturday, and it includes nearly all of her vast inventory of 20th-century American graphics. There are thousands of prints, all reduced by 10 to 20 percent, by 60 of Haslem's regular artists, among them Corita Kent, Carol Summers, Mark Tobey, Antonio Frasconi, Misch Kohn, Mauricio Lasansky, Gabor Peterdi, Grant Wood and John Sloan. Hours are today and Saturday, 11 to 6; and Friday, 11 to 9 p.m.