Sarah Tuft has provoked public thoughts about private matters since her student days at the Corcoran School, when she first appeared as "Lady Sarah"--the teen-age model for a billboard-size cheesecake painting placed at a local construction site by Corcoran artist Bill Newman. After announcing that Tuft's bikini would wash away with the first rain--leaving Tuft in the buff--Newman was asked to remove the painting lest public passions overheat.

Now a teacher at the Corcoran School, Tuft recently has been making shadowy, melodramatic paintings of nude mothers and pubescent daughters, sometimes alone, sometimes together, almost always cavorting on beds. They are on view at Gallery K. Deliberately ambiguous, these ominous oils (based on Tuft's own photographs) are loaded with sexual overtones of a most unsettling sort: Are these adults cuddling these children, or are they about to molest them? In the strongest work, "Disentanglement (from Mother-Daughter Series)," it is not even clear that the nude, encircling "mother" is not, in fact, a nude father. If so, this is no ordinary daddy-daughter romp.

Rendered in tones of black and gray, with touches of ghoulish red, these paintings hang alongside black-and-white photographs similar to the ones she based the paintings on. Viewers are likely to wonder what the paintings do that the camera has not done better.

The paintings heighten ambiguities of the Surrealist sort--double images, eerie, floating movement and so on. But the highly erotic photographs are far more eloquent expressions of the sensual woman-within-the-child--if that is her goal--than the paintings, which often come off as shallow titillation.

If one is angered by Tuft's attempts to manipulate her images--not to mention her viewers--to achieve nothing more than an unspecific sense of the bizarre, it must be said that she is in good company these days. New York artist Robert Longo heads a long list of figurative artists who have taken the same route, though it is angst, not sex, that is his stock in trade. Washington painter Joe Shannon's erotic psychodramas also come to mind, though his work is more deeply felt.

In the end, Tuft comes across here as a superior photographer, a good draftsman and an ambitious painter who still needs to find significant subject matter. To her credit, this work is hard to ignore, even though the initial impulse may well be to leave the room. The show will continue at 2032 P St. NW through April 23. Hours are Tuesdays through Saturdays, 11 to 6. Sirpa Yarmolinsky

In her new show at Plum Gallery, the inventive Finnish-born Sirpa Yarmolinsky continues her search for worthy new modes of expression. Out of two tries she has come up with one worth pursuing.

Known worldwide for her wall-hangings and woven sculptural forms, Yarmolinsky has followed many directions since her 1978 show at the Textile Museum, wresting excitement even from the unlikely medium of tar paper. Like many of her contemporaries she has been seduced recently by the possibilities of handmade paper made from her own linen yarns. Given her lyric touch and poetic way with color, it is no surprise that she has produced works of exquisite delicacy and hue.

These are no mere blobs of pressed pulp--a too-common occurrence these days. Using a square-within-a-square format, she has embedded bits of fiber between layers of colored pulp, producing pale chromatic overlays and transparencies, along with the flurry of dancing forms seen in "Choreographic Notations" and "Diary of a Magnet." Restrained use of colored pencil and silver ink further animates the surfaces.

There are also several framed, wall-hung pieces made from paper rope and linen yarns woven on the diagonal, with paper fragments attached to the surfaces. These are repetitious works that seem to aspire to be paintings.

The show continues at 3762 Howard Ave., Kensington, through May 10. Hours are Tuesdays through Saturdays, 11 to 4.