WITH "Durer to Delacroix: Great Master Drawings from Stockholm," the National Gallery continues to educate our eyes to the spontaneous line and deft touch of the old masters.

Italian, French, Netherlandish, German and Swedish, the 118 drawings come from the Swedish National Museum and include works by Rembrandt, Rubens, Raphael, van Dyck, Goya and Watteau. They are shown rarely, because of their fragility.

"If you put them up on the wall, they fade and disappear," says Per Bjurstrom, the Swedish National Museum's director. "Our climate is not always agreeable for men," he says, "but it is for drawings. It's cold and dry and dark."

That is the explanation he gives for the extraordinary quality of the drawings. Many of them were collected in the 1740s by an eager connoisseur named Carl Gustaf Tessin. Financial troubles forced Tessin to sell the drawings in 1755 to the king of Sweden. In recent years, Bjurstrom has attempted to fill the gaps in the collection, which ranks among the giants in graphic arts.

Though they may be fragile, the drawings are intensely expressive -- especially the portraits and facial studies. While Ghirlandaio's "Head of an Old Man" was probably drawn after the old man died, the Florentine still captured the grotesque bulbous nose and hence something of the man's life. Portraitist Francois Quesnel found the "Grand Duchess of Tuscany" to be a haughty 17-year-old in her stiff ruff. And van Dyck's two drawings here, portraits of his contemporaries, could only have been perfect likenesses of a merchant and an unidentified "Middle-Aged Man," they are so real.

Arranged chronologically, the exhibit makes for complementary couplings -- such as Watteau's "Portrait of a Young Man" hanging beside Rembrandt's "Seated Old Man." Both men look down, leaning to one side. But the young man has the careless freshness of face that says he is either reading an amusing story or caressing a woman's hair; the old man, with wrinkled brow, is possibly engrossed in his devotions -- prayers of desperation. Both drawings are fluid, done in red chalk, but the hatchings and shadings of the two artists are as different as their signatures.