PATRONAGE OF artists is an ancient and continuing tradition in the Catholic Church. Works by two devout and delightful young members of the faith go on view Saturday at Washington's Paul VI Institute for the Arts.

Deceptively simple watercolors by an anonymous Japanese Carmelite nun gradually reveal themselves to be subtle exercises in Oriental iconography. Paper sculptures by Baltimore seminarian David Chang recreate the short and hectic history of America's first monastery, at Port Tobacco, Md.

The cloistered creator of the watercolors, who remains nameless by choice, is a mainstay of the Tokyo Carmel. Her stylized Madonna and Child scenes become Christmas cards (available at the exhibit for $1 each) that provide much of the monastery's income, but they have nothing in common with the treacly dreck found on drugstore card racks.

The nun's haloed Mary and Jesus are virtually nonpersonified symbols, pure but perfunctory shapes with which viewers may invest as much or as little meaning as their religious or secular viewpoints dictate. The broader appeal of the paintings lies in their composition, colors and details. Remove the figures, or subsitute non-Christian ones, and these watercolors would stand as fine examples of modern Japanese classicism. Since the talented sister accepts neither compensation nor recognition, it is art for art's sake, or rather, for His sake.

Chang's paper sculptures are pretty, witty and wise. Commissioned in commemoration of the bicentennial of the Monastery of Mount Carmel, they chronicle the landing of the priests and nuns in 1790, the vicissitudes of establishing a headquarters for the ancient contemplative order in a rude new land, and such memorable incidents as The Day the Livestock Fell Through the Ceiling.

After 40 years during which the howling wilderness around them grew into a rowdy seaport, the Carmelites removed to the more genteel precincts of Baltimore. The tide of history flowed on, and in 1976 members of the order abandoned turbulent Crabtown and returned to the bucolic backwater of Port Tobacco.

MY GENTLE MADONNA and PAPER SCULPTURE BY DAVID CHANG -- Saturday through Nov. 3 at the Paul VI Institute for the Arts, 924 G St. NW. 347-1450. Open 10 to 5 Tuesday through Saturday. Metro: Gallery Place. Wheelchair users should call ahead for assistance with the front steps.