In 1967 John Duff and his friend from the San Francisco Art Institute, the painter Gary Stephan, left California for New York City, looking for a more supportive and expansive atmosphere for making art. They landed in the creative milieu of 76 Jefferson Street, a legendary art loft building on the Lower East Side where their neighbors included the artists Melvin Edwards, Janet Fish, Neil Jenney, Valerie Jaudon, Brice Marden, and Robert Lobe. Duffs quirky abstract sculpture soon became a key component of the so-called post-Minimalist movement, and his work was exhibited in the company of artists such as Richard Tuttle, Carl Andre, Richard Nonas, Lynda Benglis, and Barry Le Va.

John Duff’s Green Stripe, 1972, speaks of the elation of color, a lyrical acid green and the imprecision of any edge, wavering as it defines what appears from a distance to be a neat vertical line. Art historically minded folks might recall Barnett Newman’s “zips,” his legendary vertical motifs that were supposed to make one think of God. Duff’s Green Stripe is more singular and enigmatic, not universal and pulsing with colossal power. Perhaps, the closest it gets to God is in evoking, loosely, the elusive “green flash,” an atmospheric effect that is reputed to occur—if you look closely enough—at the horizon precisely before sunrise or immediately following sunset. (I’ve looked and looked but never seen it happen.)

Similarly, Duff’s playful Orange Concatenation, 1980, seems on the verge of solving some problem in geometry but then loses the thread and ends up being only—but marvelously only—about itself. An array of triangular elements, composed of fiberglass and orange pigment begin, from the left, to describe the lower half of a circle, then suddenly change direction, flip around, and like a breaking wave, hurry off the other way with better things to do. What fun is being a Platonic form when you can be something unpredictable and weird? The whole assemblage is attached to a long horizontal piece of bare wood. Why? “For support,” says Duff.

Duff continues, “Everything in nature is like that. One thing supports another.” Nature has always been Duff’s guide, not art history or someone’s abstract ideas about structure and plasticity. Though he grew up surfing in Southern California, since moving to New York City in 1967, his experience of nature has been somewhat more abstract, deductions based more on principles than observation. He is drawn particularly to physics and geometry, fields that—like his own practice—allow one to extrapolate variation from a universal premise. Duff sees art in terms of evolution, building on itself in a succession of approximation. The things that work survive. (It’s interesting to know that Duff has continued to make ceramics since the late 1960s when his teacher at the San Francisco Art Institute, Ron Nagle, “pulled the rug out from under [him]” but hasn’t shown any until very recently, because “they didn’t have what sculpture needs.”)

Duff’s “wedges,” such as Untitled (Wedge), 1983, are comparatively mute with smooth, arcing surfaces that deflect the impulse to project too much character or personality, though some critics have suggested a figurative reference in their human scale. Perhaps one can see in them a faint allusion to wings and, indeed, they do possess something of the auratic quality of Bruce Conner’s Angel photograms. But to Duff, there’s nothing mystical to see here, just an exploration of materials and geometric typology. In purely formal terms, what makes this work a “Duff” is the contrast of idealized shape and irregular surface, the tension between opaqueness and transparency, and the impregnation of the wedge with a sly little hole.

Holes, though filled this time, are also central to a later work, Five Materials in Combination II, 2003. Circular sheaths hold fractured columns of various materials: cement, resin, wax, rubber, and steel. The combined elements are arranged in a triangle on the floor like neatly toppled bowling pins. Indeed, one feels there is something game-like going on, a rock-paper-scissors-ish sequencing the logic of which, like much of Duff’s motivation, remains devilishly obscure.

• Larry Rinder