Ian McKellen's pliable features can create characters of any age, size, or even sex on stage; offstage they freeze into an unfriendly mask of disdain. He stares with objective interest at a pair of women chattering in a restaurant, noticing the elaborate neatness of their hairdos and makeup.

At the entrance of an expensive downtown restuarant he surveys the dining room and says, "Don't they let black people in here?" Half an hour later he withers a pushy waiter with a look so icy it would freeze alcohol. He wears dark trousers, a striped shirt, a conservative tie, a pale yellow windbreaker, black shoes--and white socks.

The last time McKellen was in Washington, he was playing the part of Salieri in "Amadeus" at the National Theatre. He went on to win a Tony last year after the play moved to Broadway, and for the last few months has been back at home "recuperating." He returned to help the Folger Shakespeare Library with its 50th anniversary and to talk about "Ian McKellen Acting Shakespeare," a delightful 90-minute show to be aired tonight at 9 on Channel 26.

McKellen's intention is to infect the audience with his enthusiasm about Shakespeare, to deflate some of the intimidating pomposity that usually surrounds performances of his work. That McKellen accomplishes this without resorting to the patronizing familiarity that often passes for "making Shakespeare real" is a tribute to his skill. It is, of course, easier to avoid boredom with a one-man smorgasbord, culling speeches that stand alone without having to deal with the stuff in between. But McKellen adds a dimension with personal anecdotes, theatrical gossip, and a fascinating analysis of Macbeth's "to-morrow, and to-morrow, and to-morrow" speech as he prepared it for performance.

His own breakthrough in dealing with Shakespeare came fairly early in his career, while playing the part of Aufidius in "Coriolanus" at a small theater in England, directed by Tyrone Guthrie. Aufidius or his allies kill Coriolanus, and immediately afterward he gives a speech of regret ("My rage is gone/ And I am struck with sorrow . . . ").

"Most actors interpret this with an ironic twist," he said. "But Guthrie wanted me to play it for real, and he wanted me to keen over the body, or find a noise that expressed this anguish. I couldn't do it. He came galloping down the aisle, this enormous man--6 foot, 6 inches--stopping the rehearsal. He said: 'Now come along! We're all waiting! You've got to do it full out, you've got to believe it! Now come on!' It was said in a schoolmarmish way, but more that it was my duty to match up to this wonderful piece of theater which will, if it works, galvanize the audience . . . Enthused by him, I did it, and found he was right.

"I found acting Shakespeare much easier after that."

He began to build his reputation as a "classical" actor a few years later, when he was 31 (he is now 42). He's played Hamlet, Leontes, Macbeth, Toby Belch and Richard II during four seasons, starting in 1974, with the Royal Shakespeare Company. In his one-man show he adds a credible Juliet and a touching Mistress Quickly and Falstaff to this list.

"Romeo is really a terrible part," he said. "We all think we want to play it because the play is called 'Romeo and Juliet,' but it's really Juliet's play."

The sentiment is borne out in the show; his Romeo is rather bland and unconvincing, while his petulant Juliet is far more interesting.

"I am constantly looking for the modern parallels in these plays," he said. "You know, it's a false idea that when you do Shakespeare you'll find out what it was like in Elizabethan England, or what it was like during the reign of Richard II. There are plenty of historical plays but generally the point is to make a comment on life today. Even a play as bad as 'A Lion in Winter' is trying to say something about our time.

"I always have pockets in my costumes. And I want to know what's in them. Coins? A credit card? Nothing? Perhaps a hole?"

The Shakespeare show began in 1976 as something to take to the Edinburgh Festival. Since then he has performed it for fund-raisers, including two in New York during the run of "Amadeus," one for the group that is trying to rebuild the Globe Theater in London, and another for a small New York theater that stages only plays that have failed the first time out.

Ironically, his last appearance in London was not in a classic, but as Max in the controversial play "Bent," which dramatizes the plight of homosexuals in Nazi Germany, who were sent to concentration camps and forced to wear pink triangles. The part was written with McKellen in mind, as he learned from the playwright on opening night.