Contemporary art collectors in Washington often explain their frequent buying trips to New York with a complaint: Washington galleries, they insist, don't provide the stimulation of their New York counterparts, which are testing grounds for ideas. Only in New York, they say, can they be challenged, educated and ultimately become literate in the visual language required to understand new, nontraditional art.

Chris Middendorf, one of the few dealers in town who consistently challenge Washington audiences with new ideas, heard the complaint once too often, and his retort was to challenge complaining collector Thea Westreich to fill his gallery, top to bottom, with the sort of show she'd like to see here more often. The energetic Westreich, a noted contemporary collector and public relations consultant in the arts, took up the challenge, and "The Hidden Surface," now at Middendorf, is the result.

It is a modest show that even Westreich probably wouldn't travel to New York to see. But it also is thought-provoking and offers a useful framework for looking at the eight varied artists she has selected to make her point.

Though there is a distinct tilt toward the postminimal, postconceptual art Westreich favors, the common denominator clearly is not style. And it surely isn't quality, which fluctuates wildly. It is a theme: "The artists' concern with surface and how it affects the viewer," as Westreich defines it in her informative, well-researched essay on the show. "The surface becomes the conduit for this discourse."

Discourse seems pretty unlikely when the first thing you notice looks like a curled piece of thick gray felt accidentally dropped in the middle of the gallery floor. Closer inspection reveals it to be a cast lead sculpture by young New York artist Roni Horn, the only interesting newcomer in the show. Its title, "Mass Removal," refers punningly to its placement on the floor (a mass that needs removing), but more seriously to the sculptural process by which it has been formed (the removal of the interior mass, as evidenced by its gouged-out surface).

The theme prods the viewer to examine surfaces of other seemingly forbidding works for messages or impact: to approach them, in other words, with an appropriate question ("What does this surface tell me?") rather than with uncomprehending disdain. No single work makes Westreich's point about the power of surface better than the late Yves Klein's vibrant "Venus Blue" from 1970, which zaps you in the eye at the top of the stairs. Nothing more than a plaster cast of a classic torso painted a color known as "international Klein blue," it radiates disembodied color against the surrounding white walls. Klein's view was that color can electrify the space around it, and he proves it here as effectively as he ever did.

There are vividly colored day-glo abstractions by Peter Halley, but they pale beside Klein's work, despite Westreich's vain attempt to give them some kind of philosophical heft in her catalogue essay. Likewise, no amount of florid philosophizing -- even in the form of quotes from the artists -- can salvage from utter superficiality the seemingly mildewed black painting of Christopher Wool, the cement-surfaced canvases of fledgling painter Joyce Pensato or the utterly irrelevant photographs by Kathryn Zoe Leonard on the third floor.

Though Westreich seems to have run out of steam two-thirds of the way through her selection, the show's low points serve an important purpose: By sheer contrast, they highlight the ability of the good artists here -- even those we may not fully understand. The recent painting "Container," by minimalist Robert Ryman, for example, may seem hermetic and elusive at first, but after all the other "Hidden Surfaces" in this show, his creamy white paint over textured fiber glass has an eye-cleansing purity. It is a classic, if unintended, lesson in connoisseurship.

In the end, Westreich makes a point: Recent works of art presented in thoughtful ways by thoughtful curators can be most illuminating and provocative. But she also thereby reminds us how often such a thoughtful approach is taken in Washington museums: in the "Spectrum" series organized by Ned Rifkin for the Corcoran, or the "Content" and "Directions" shows at the Hirshhorn, or in any number of shows at WPA -- and sometimes in galleries as well.

As to the shortcomings in commercial galleries, it is selling -- not teaching -- that is their purpose, and they tend to show what people are likely to buy, or at least eventually show some interest in.

But Westreich is right: It is in galleries that the great schism exists. In New York, trendiness is next to godliness, which is manifest in Leo Castelli, and people line up -- and pay up -- to get a smile and a handshake from the latest purveyor of the avant-garde. Washington is more skeptical, and dealers more cautious and conservative, at least in some small part because the major collectors here so often leave them stranded, and go off to New York to buy their art. This situation, happily, is now changing as new real estate wealth pours into the city.

No question: New York galleries are far better able to stay au courant, because they are au courant by art world definition. But is it trendiness that people really want, or is it quality and understanding? Westreich notes that Washington misses out on the flow of ideas that moves through New York galleries, but the more discriminating might say that's something to be grateful for.

As for Westreich's complaint about not seeing enough new art in Washington galleries, let it be noted that this was her big chance to bring it here, yet the best work in the show turns out to be Klein's "Venus Blue," a piece a modern master made 16 years ago.

And by the way, when's the last time a New York dealer told a collector to put up or shut up? Middendorf might consider making this an annual event and call it the collector's challenge.

"The Hidden Surface" will continue at Middendorf, 2009 Columbia Rd. NW, through June 14. Hours are Saturdays, 11 to 5, Tuesdays through Thursdays, 11 to 6.