In an essay published in Artforum in 1986 and included ten years later in his book Kant After Duchamp, Thierry de Duve proposed that the ready-made— Marcel Duchamp’s innovation of treating an everyday, industrially produced item, such as a bottle rack, snow shovel or urinal, as an art object—“ought to be reinterpreted today in connection with painting.” De Duve’s suggestion has been more or less ignored: in theory, if not in practice, painting and the ready-made have pretty much gone their separate ways. But I still think de Duve was onto something.

Seeing “Inventing Abstraction,” the fascinating exhibition currently at the Museum of Modern Art—in which Duchamp is a signal presence, although not as the proponent of the ready-made [see “Wild Things,” March 11–18, 2013]—has rekindled my interest in de Duve’s claim that “the birth of abstract painting is the relevant context” for the appearance of the ready-made. True, de Duve was too credulous of the many witty remarks Duchamp made a half-century after the fact, justifying his recourse to the ready-made as a retort to the situation of painting in an industrial age. In 1961, for instance, Duchamp stated at a symposium on assemblage: “Since the tubes of paint used by the artist are manufactured and ready-made products we must conclude that all the paintings in the world are ‘readymades aided’ and also works of assemblage.”

What Duchamp cleverly avoids confronting, except for the acknowledgment hidden in that innocent little word “aided,” is the unique and unindustrialized nature of the human gesture by which that industrial, ready-made product, paint, may be applied to a surface. This gesture “aids” the paint considerably, at least in the most favorable cases—though, admittedly, it may be a struggle to achieve this. How else to explain the wit and pathos of Frank Stella’s remark that his goal was to keep the paint as good on canvas as it was in the can? Stella was 27 when he said that, and young as he was, he already understood how easy it is to spoil good materials: just breaking even was already to be ahead of the game.

Giorgio Griffa, an Italian painter who recently had his first show in the United States since 1970, might just as well say he’s trying to keep the canvas as good on the wall as it was on the roll. For any painter, the choice of a painting surface is crucial, but more so for Griffa than most. For him, there’s no such thing as a blank canvas, because the canvas itself is a ready-made, an industrially manufactured material thick with information integral to the finished painting. Griffa would probably contest my use of the word “finished.” Myself, I’d start instead by taking issue with the word “canvas,” which is how the checklist at Casey Kaplan Gallery in New York City named the material on which he’d applied his acrylic paint in all the works included in the exhibition “Fragments 1968–2012.” But the “canvas” is really several different kinds of textile, of diverse hues and textures; several of the paintings were done on a dark, coarsely woven jute fabric.

Griffa’s canvases (or whatever it would be more precise to call them) are not stretched but simply pinned to the walls. And even if he had never put a spot of paint on them, each one would already be a little different from the rest—and not only because of the innate qualities I’ve already mentioned. There are also the more or less rough and uneven edges where the canvas has been cut, sometimes leaving loose threads hanging here and there, and especially the deep horizontal and sometimes vertical creases most of them bear from having been folded and unfolded. These textures reflect the manner in which the canvases are stored when not being exhibited—and so with Griffa’s work, even storage has to count as part of the activity of painting them, because it’s clear that each piece is folded in its own way in order to create a grid of specific proportions, with folds of a given depth.

Are these folds made before Griffa starts to paint, or after? It’s a question that one of the paintings on view poses directly. Linea spezzata (1970) bears three horizontal zigzags, purple, violet and peach, each of which crosses one of the horizontal folds in the canvas. It’s the central violet zigzag that’s the “broken line” of the painting’s title. What breaks it is the fold, a sort of valley into which Griffa’s acrylic paint has not penetrated. So this fold, at least, was made before any paint was applied—but that doesn’t reveal anything about when the other two horizontal folds were made, or any of the vertical ones. What it does suggest is that for Griffa, a painting is, before anything else, “a marked-up surface”—a phrase of Clement Greenberg’s from his essay “Modernist Painting.” But the surface is marked before the artist ever applies any paint to it, and the convention that the surface should be flat is nothing more than a holdover from the old illusionism. It might be true that “realistic, naturalistic art had dissembled the medium, using art to conceal art,” as Greenberg claimed, whereas modern art acknowledged and indeed exalted its medium. But stretching the canvas around rigid bars, smoothing out any folds or dings—when, at least from Jackson Pollock on, painters had become more and more likely to paint on unstretched canvas—would be once again to conceal the medium. In a painting on canvas, Griffa reminds us, the canvas is as much a medium as the paint.

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It might seem that I take Griffa to be engaged in a polemic on the theory of painting, or perhaps a quasi-pedagogical demonstration of why he is the only artist not to have sunk into the mire of an unacknowledged traditionalism. And it’s true that at one time, in his younger days, there was a polemical edge to his manner of painting. That edge glistens in the title of Griffa’s 1972 solo show in Rome, “Io non rappresento nulla, io dipingo” (I don’t represent anything, I paint). He’s right: he doesn’t represent. He paints by laying out the matter of painting—canvas and marks on it, only some of which are made with paint. And the traces of paint on his canvases tend to be pretty sparse. You might think he was following some apocryphal adage of aesthetic parsimony: “He paints best who paints least.” Yet if his aim were simply to give a purist demonstration of the minima of his art, he could easily have limited himself to exhibiting variously folded canvases, or perhaps only ones in which the painted marks had some overt interaction with the fold, as with the violet zigzag in Linea spezzata. But at bottom, Griffa’s is a sensual art more than an intellectual one. Yes, he reduces painting to just a few basic elements, but for a reason: to show color in all its glory.

Perhaps this appearance is a sort of representation after all. These days, Griffa describes his art differently: “It is another morning in the endless representation of the world, where knowledge and seduction are stored.” His language may have changed, but his sensibility has always been consistent. It’s hard not to be seduced by the solar intensity of a painting like Obliquo giallo (1971). The piece’s series of yellow slanted lines—or backslashes, as we’ve since learned to call them, placed on the canvas in a hand that is neither expressive nor mechanical but simply relaxed and concentrated and, above all, focused on getting the job done—work together, and the atmospheric space allowed by the quantum of white canvas separating each line from the next creates a concerted blast of painted sunshine. This unabashed appeal to the senses is a constant in Griffa’s art; what may be more surprising is how his more recent paintings display an equally forthright sense of fun.

It can be seen, for instance, in his homage to Daniel Buren, a fellow painter of Griffa’s own generation, who since the late 1960s has made his art out of the reiterated use of a single motif: stripes of exactly 8.7 centi​meters, sometimes painted, sometimes printed. (By coincidence, there have just been two excellent shows of Buren’s work in New York, at Petzel Gallery and Bortolami Gallery.) Griffa’s painting DDB (Da Daniel Buren) (1997) is made of four squarish canvases, each with a single horizontal fold across its center. The first two canvases on the left, and the left half of the third, are marked with vertical stripes of purple and violet alternating with bands of unpainted canvas, in overt evocation of the (inevitably more precisely ruled) stripes that Buren uses. Starting toward the right of the first canvas and continuing from there across the whole field of purple and violet bands, some narrower lines of blue begin to appear, coming down from the top edge of the canvas; each blue line is longer in the sequence from left to right, and after the last of the “Buren bands,” there are three more blue lines in the right half of the third canvas and the otherwise unpainted field of the fourth. The first of these three blue lines curls up a bit at the bottom, the second has still more of a curve to it, and the last one—crossing the gap between the two right-hand canvases—floats there with the sinuous languor of a cat’s tail, supported, at its tip, by the three letters of the painting’s title.

Griffa undoubtedly sees Buren as an estimable colleague. Both started out with an austerely analytical approach to painting, somewhere in the neighborhood of minimalism; and, without ever changing course, both have ended up acknowledging that, in Buren’s words, “Art has never ceased being concerned with decoration.” But Buren has never ceased being serious, and in DDB (Da Daniel Buren), Griffa, even as he pays tribute to his brother artist, is also teasing him, introducing that capricious little blue line with its irrepressible tendency to deviate from rectitude as a witty foil to Buren’s rational and regimented stripes. The insistently reappearing line bothers the stripes for a while like a mosquito in their ear, then goes its own way, perfectly content.

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I couldn’t be happier to have finally discovered Griffa—one of the best painters of our time, pushing 80 and new to me. But happy surprises can just as easily turn up closer to home. After spending some time at Thomas Nozkowski’s current show of new paintings (and, as a bonus, a selection of his works on paper) at Pace Gallery in New York, through March 23, I revisited his biography to remind myself how many exhibitions of his work I’d seen. Since 1984, there have been about twenty—mostly in New York, a few in London. Across that time, his work has remained consistent in its sensibility, though within the parameters of that consistency, it has also been curiously diverse. Most consistent of all has been his commitment to painting on a small scale, so that the appearance in the current show of a couple of works as large as thirty by forty inches suggests that something in Nozkowski’s work has experienced an upheaval—one he’s negotiated with aplomb.

How to explain the inner dimensions of this artist’s consistency, though—how to say what makes a Nozkowski painting so recognizably a Nozkowski—is more of a challenge than simply saying that small is beautiful. Whereas Nozkowski is just as unswerving an abstractionist as Griffa, his sense of abstraction is entirely different. Griffa presents each trace of paint as a separate and distinct reality, touching only the canvas surface that also exists as a distinct reality while serving as a home for those separate but equal marks of paint. “Mine is the painting of a world that comes into being as I do it,” Griffa has said, which means that the traces his actions leave refer in the first instance to themselves; this is true even when those traces can subsequently be compared to the motifs associated with another painter, as in the case of his citation of Buren, or when they form numbers or letters, as is increasingly the case in his more recent work.

Nozkowski’s paintings, by contrast, are connected to a world that already exists, though only in the mind’s eye of their maker; they are made not to display their own material elements, but to use those materials to picture things one hasn’t yet seen: the inner world has its ready-mades, too. Greenberg once dismissed this sort of painting as “homeless representation,” a “plastic and descriptive painterliness that is applied to abstract ends, but which continues to suggest representational ones.” In the critic’s eyes, that homelessness was the ruination of many an Abstract Expressionist, from de Kooning and Guston on down. Nozkowski is no Abstract Expressionist: among the great modernists, his affinities are with playful and poignant miniaturists like Paul Klee or hard-headed poets of the quotidian like Giorgio Morandi (though there’s also something deliciously cartoony about his irregularly indulged penchant for heavy outlining). But like de Kooning and Guston, and contrary to Greenberg, Nozkowski makes homeless representation look very good.

Nozkowski paints visual conundrums that involve abstract forms flowing into representational ones, flat geometrical patterns into volumetric shapes and back again—just as affection can flow into anger and back, or excitement into lassitude and back. It’s this constant sense of change, flow and readjustment that is the truth of one’s subjective existence, and so it would be false to fix on one realm of feeling as the rock-bottom existential truth. Although we call it abstraction, this endless chain of Ovidian metamorphoses just might be what Griffa meant by “endless representation.” In Nozkowski’s paintings, distinct kinds of visual material are juxtaposed, and yet the juxtapositions seem to fold in and out of each other in mysterious ways—one pattern functioning as the background to another, for instance, until you suddenly notice that they can be seen switching roles, the background shifting to the foreground.

Nozkowski’s paintings always have surprises in store, if you keep looking; things in them tend to remain in flux, to interact in unpredictable ways. But what makes this exhibition a happy surprise is something else: the sense that Nozkowski’s already expansive vocabulary of abstract forms and pictorial “moves” has expanded even more. Almost every painting has some odd little detail, some unexpected way of putting the paint down, some scheme for introducing incompatible forms without provoking a fight between them, that I don’t recall noticing in previous exhibitions of his work. It’s amazing to see, in the painting designated Untitled (9-20) (2012), how he’s availed himself of soft, hazy hues that remind me of melted crayons; in the hands of almost any other painter, they would seem insufferably sentimental. In Untitled (9-7) (2011), he’s conjured a pair of bulbous yellow quilted forms that look like a cross between the bleary-eyed, disembodied Cyclopes that inhabit Guston’s late works and a couple of baseball catcher’s mitts, and placed them against a ravishingly delicate ground of red dots evocative of the early work of Yayoi Kusama. Amazing too is the way the geometrically patterned spherical form that dominates Untitled (9-15) (2012)—at once huge like the Unisphere in Flushing Meadows–Corona Park and tiny like a golf ball—is handily flattened by the irregular strips of brown and blue that cross in front of it. Nozkowski keeps seeing new things in painting and making me see them, too.

Barry Schwabsky looked at the latest Manifesta and Documenta art exhibitions last year.