One of the best-kept art secrets in town has been the thriving printmarking shop on the ninth floor of 1900 L St. NW -- headquarters of the Graphic Arts International Union. There, for the past five years, the union has quietly maintained a lithography, etching and engraving workshop where artists could go to learn -- and to print their own handmade editions for a blushingly modest fee.

Now, for the first time, a show of prints by the artists who've taken that opportunity has been hung on the workshop's walls. It will be open to the public every day until Christmas, and a lunch-hour visit could make holiday shopping both painless and instructive.

"Union Printmakers," as the atelier is called, came about by chance after Washington artist Scip Barnhart visited the American Folklife Festival on the Mall in 1974. He happened upon GAIU members demonstrating what they considered to be the defunct art of stone lithography, a method used in the days of Currier & Ives, but long since supplanted by photo-offset techniques. "They knew nothing of the '60s revival of interest in the medium," says Barnhart, who hard been studying lithography at the University of Maryland. "I suddenly realized that there were probably 120,000 members of the union -- including many old-time stone lithographers -- who thought the medium was dead!"

With the help of his friend and staunch supporter John Stagg -- education director of the GAIU -- Barnhart developed the idea of setting up a workshop that would serve in effect as a working-museum of stone lithography, as well as a place where industry artisans and contemporary fine artists could exchange ideads. "All I needed was space," says Barnhart, and the union obliged. It offered a large, sunny space in its downtown office building (which would cost $20,000 per year if rented out), and put in a $3,000 sink. This year the union provided a grant of $6,000 to help pay for supplies. Six presses, including two etching presses and one small relief press, have been variously begged, borrowed and bought.

"GAIU also helped us acquire some very large lithographic stones at a very modest price. I thought I'd gone to lithographer's heaven," says Barnhart, who receives no salary for his workshop efforts and supports himself in part by teaching a printmaking class from George Washington University at the atelier. The space is also available 24 hours a day to any responsible artist who will abide by the rules. The fee of $35 per month includes the use of two small lithographic stones.

The present show is injuried, and the work ranges from very good to indifferent, with Barnhart's own black-and-white lithograph, "Asleep on the Wing of the Angel of Death," among the most striking examples. Also tops are John Dreisbach's drypoint and aquatint" Jogger's Delight," Francoise Yohalem's fine constructivist abstractions, Penelope Barringer's organic, linear forms and the anthropomorphic chairs of Linda Hendrick. Caroline Thorington, known for her zoo images, is represented here by a romping rhino, while Richard Blackmore and Susan Schmuhl are the newcomes of note. Prices are modest: $30 to $200. Hours are 9 a.m. to 2 p.m. every day, including Saturdays and Sundays, until Christmas.

One of the area's best-known spaces for buying and watching work-in-progress is Printmakers Workshop on the second floor of the Torpedo Factory in Alexandria. It should not be missed by anyone in search of a wide variety of top-notch reasonably priced, handmade prints.

The workshop is currently celebrating its fifth birthday with a holiday show (though January) that includes works by the 11 artists who share the space. Featured are several winning woodcuts from Phyllis Cohen's recent book "Applesauce" (one was included in the Corcoran Area Show); etchings and monotypes by June Hoke; handmade paper and silkscreen pieces by Betty Kubalak; etchings and woodblocks based on Oriental rugs by Nancy Reinke; and wonderful little handmade books by Barbara Romney. Prices range from $20 to $300, and the workshop-gallery is open from 11 a.m. to 5 p.m. every day, including Saturday and Sunday.

Lou Stovall's Workshop Inc. -- one of the finest silkscreen workshops on the East Coast -- has, over the years, produced editions by many of Washington's better-known artists, among them Sam Gilliam, Gene Davis, Sidney Guberman and proprietors Lou and Di Stovall. Some prints by each of these artists are still available at the workshop, 3145 Newark St. NW, and can be purchased there by appointment.

ANTX Hill Workshop -- the first in Washington devoted to promoting and supporting black professional artists -- was founded a decade ago in an inner-city row house by painter Ron Anderson and photographer Teixeira. Though they no longer share working space, the original group still shows together, and they are now appearing on the ground-floor gallery at AFSCME headquarters, 1625 L St. NW.

Ed Love is the standout here with several welded chrome sculptures. He has reworked automobile parts into provocative forms that recall African sculpture. Frank Smith's stitched and painted canvas collages -- stretched to look like dried animal skins -- also effectively combine contemporary American art with African sources. Much of the work is both angry and political, one of the most successful examples being Donald S. Benjamin's poignant Xerox collage titled "How Soon We Forget." The show continues through Jan. 30 from 9 a.m. to 6 p.m., Monday through Friday.

And those looking for some of the best contemporary American art seeking to incorporate African sources should not miss the current faculty show at Howard University Art Gallery. It is, as always, a first-rate exhibition by one of the most inventive art faculties anywhere.