When ceramic artist Gertrud Natzler died in 1971, friends worried about her husband.

Gertrud and Otto Natzler were among the most admired and influential of 20th-century ceramic artists, with works in the Museum of Modern Art, the Smithsonian and virtually every other important collection of modern ceramics.

Since their relationship began in Vienna in 1935, the two self-taught artists fled Hitler, moved to California and jointly produced 25,000 pieces, always with a strict division of labor: Gertrud threw on the wheel the exquisitely thin, classic bowls, vases and bottles, and Otto devised and applied his unique glazes and fired them.

The Natzlers were as bound as the forms and surfaces of their ceramics. What would happen to Otto now that Gertrud was gone?

The answer can--and should--be seen in "Otto Natzler at 75: Recent Works," now at Franz Bader Gallery.

After Gertrud's death, Otto set out to finish the 200 unglazed pots she had left behind, but with the "frightening" realization that the supply was finite and the collaboration had to come to an end. In 1976 he gathered his courage and began making his own forms in clay.

Though a dozen of the posthumously fired, collaborative pieces are on view (feather-weight bowls, a chalice of luminous cobalt blue), Otto Natzler's new work holds its own--in large part because it does not challenge the past.

For one thing, Natzler could put one of his 2,400 incredible glazes on any pot and make it worth looking at. There is a wholly undistinguished spherical form in this show, but it is covered with a dramatic, heavily textured, iridescent glaze so full of life visitors can't keep their hands off it.

Natzler also proves himself to be an able form-giver, producing bolder, far more sculptural vessels than Gertrud did--and taking more risks in the bargain. Inevitably, some of the shapes turn out to be less than perfect, especially some of the standing discs and their arrowhead-like variations, which still seem experimental.

The best pieces, however, are very strong, sustaining the integrity of the rectilinear slabs from which they are made, producing boxy forms--fat cubes and tall rectangles, some of them highly architectural. One of the most dazzling is a small monolith with a pitted surface that looks for all the world like corroding bronze, the result of the spectacular "crater" glaze that has become Natzler's hallmark. Surface and form are inextricably wed here, as were the best collaborative efforts from the past.

This beautifully installed show is enhanced by several color photographs that sharpen the viewer's eye to the intricacies of Natzler's surfaces and colors, which have wonderful names such as "burnt apricot," "ivory sulphur" and "mystic blue." The photos were taken by the artist's present wife, Gail. The show will continue at 2001 I St. NW through May 7. Hours are Tuesdays through Saturdays, 10 to 6. Ed Seager at Adams Davidson

In this flourishing market for 19th-century American art, every artist is of some interest to curators and collectors, even the uptight, all-but-forgotten draftsman Edward Seager (1809-1886), whose chief distinction seems to have been that he was the first professor of drawing at the Naval Academy, where he taught midshipmen to draw strategic topography. A show of his recently rediscovered pencil drawings is under way at Adams Davidson Gallery.

Though most drawings from this period are studies for oil paintings, Seager apparently did not paint (except for some overworked watercolors), and seems to have had no ambitions beyond the meticulously finished pencil views of farms, roads, mills and mountains that he made wherever he happened to be, from tranquil Maine to exotic Panama.

The problem, however, is that everything was drawn from the same objective, topographical point of view, at least until 1848, when he loosened up a bit to produce the fine views of the Cheat River in West Virginia, and the Sandwich Hills near Squam Lake in New Hampshire. These drawings alone make the show worth seeing at 3233 P St. NW. It closes May 14. Hours are Tuesdays through Fridays, 10 to 5, Saturdays noon to 6.

Incidentally, serious collectors of 19th-century American art should ask to see the recently rediscovered lode of 102 paintings, drawings and watercolors by painter William Trost Richards now being sold at reasonable prices upstairs. The works can be viewed upon request.