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John Fraser’s new mixed-media collages at the Roy Boyd Gallery are among the finest works Chicago artists have to offer. They have strength of geometry, subtlety of color, exquisiteness of balance and, every now and then, the gift of surprise.

At the core of the work are book covers and spines detached from their pages. The subject matter, content and nature of the books have not mattered. Important are the shades of ivory colored endpapers plus remnants of glue and thread inside the spines. All this Fraser adjusts in relation to various kinds of measuring sticks and, in one instance, the scroll of a violin.

The two largest pieces, almost 54 inches square, are commanding, though they still speak softly, sometimes at the threshold of audibility. The title of the exhibition, “More and Less,” could well refer to them. But there also are more small-framed collages that I recall seeing before, and these have fewer components than Fraser’s reliefs yet show no diminution of formal power.

The coldness some feel is inherent in abstract geometric art is entirely absent here. For anyone who looks closely, taking enough time for real scrutiny and noticing even the patterns caused by staples, there is a warmth and glow I find irresistible.

At the Roy Boyd Gallery, 739 N. Wells St., through Oct. 21. 312-642-1606; www.royboydgallery.com.

Michael Hernandez De Luna pursues the guerrilla activity of postage stamp and mail art. He has a hatred of hypocrisy — and exercises it. He does this on stamps he creates and gets through the mail on envelopes that have return addresses laden with irony.

His exhibition at the Carl Hammer Gallery goes off in all directions. He treats pop-culture figures, politicos, famous mistresses and, in a continuing series, female hunters of the ilk of Sarah “Barracuda” Palin. The humor in these works comes as much from their subjects’ treatment on the stamps as the envelopes that bear the examples he has passed through the postal system.

This time the artist indulges some nostalgia on behalf of Abbie Hoffman as well as LSD. These are the least successful pieces. Even lightly comic homages are not Hernandez’s forte. You expect — and look forward to — him whacking people. He is so good at it that he does not require only media figures. His plain-folk huntresses are as disturbing as anything he has done.

Some targets, such as Michael Jackson and heavyweight wrestling, are of course too easy. And the sting, even when perfectly placed, seldom lasts long. But the lack of piety is positively bracing.

At the Carl Hammer Gallery, 740 N. Wells St., through Oct. 18. 312-266-8512; www.hammergallery.com.

Dan Gamble’s paintings at the Zg Gallery are a species of fantasy landscape in which fragments of buildings or open-work metal sculptures are either being built or deteriorating. Each has a spiritualized symbol: a circular void that comes from Won Buddhism.

Larger paintings, in oils, suggest remnants of cities. Smaller ones, in egg tempera, close in on details of structures warmed by subtly colored light. Both are unpopulated.

The “built” structures within these paintings are sometimes like Claes Oldenburg’s Chicago sculpture, “Batcolumn,” in which an overall form takes shape from many crisscrossing lines. But sometimes, too, the shapes are more organic and streamlined, as if found in nature or intended for space travel. The success of Gamble’s forms depends on their allusiveness and how many things they seem to refer to at once.

The small, square egg-tempera panels are the most poetic, owing to the fragmented forms and the delicate transformative light.

At Zg Gallery, 300 W. Superior St., through Oct. 11. 312-654-9900; www.zggallery.com.

Kathleen Waterloo paints abstractions in encaustic, an old and sensuous medium. Her colors shimmer up through layers of wax to cause instantaneous seduction. But these days triggering that kind of response is not enough for artists who seek to deepen their discourse through work based as much in ideas as craft.

Waterloo’s paintings at the Melanee Cooper Gallery move in that direction. Trained as an architect, the artist here responds to buildings, imaginary (by Giovanni Battista Piranesi) and actual (by Gordon Matta-Clark, Jeanne Gang, Frank Gehry). She also pays homage to artists such as Agnes Martin and Robert Mangold, whose work has strong architectonic qualities.

In her large paintings, Waterloo’s familiar vocabulary of stripes, bars, commas and hooks is pretty much undisturbed and her architectural references are embedded within them. But a series of smaller pieces bring architecture to the fore, as shapes of the incisions Matta-Clark made in derelict buildings become primary motifs that Waterloo has superimposed on blueprints. These rely less on color and the seductions of surface, looking more improvisatory, experimental.

At Melanee Cooper Gallery, 740 N. Franklin St., through Oct. 31; artist’s talk 5 p.m. Oct. 24. 312-202-9305; www.melaneecoopergallery.com.

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