Mary Heilmann: Shadow Cup 2, 1985, glazed ceramic, 21¼ by 24 by 1¾ inches; at Whitechapel.

It was palpably clear from her Whitechapel Gallery retrospective that Mary Heilmann had initially trained as a sculptor—and not just because the earliest piece on display, The Big Dipper (1969), was a work in clay, one whose hand-molded ladle shape and blazon of tinfoil stars seemed to suggest a sort of jokey, down-to-earth materialism. Even after she began working predominantly as a painter, around 1970, her output maintained this inherently constructed, almost architectural quality, with her canvases using color like a physical thing: a lurid cornucopia of hues that can stack as stripes or tessellate as blocks or repeat in a delirious variety of modular formations.

The compositions are like puzzles, mechanical challenges. Little 9 x 9 (1973) is a small, square painting consisting of an uneven grid of lines scratched into its bright red surface, their crisscrossing overlaps encouraging you to figure out the weavelike sequence that determines the final form. The process of manufacture can likewise be divined in Little Red Boxes (1989), whose titular box shapes, encased within a checkerboard pattern of differing whites, are actually windows onto a scrubby red background, vestiges of an underlying layer that’s been all but obliterated. Other works, meanwhile, offer more of a tease or trick, such as Orbit (1978), where a glossy field of black circumscribes two triangles, one of rich pink and the other of silver, the colors visible in places beneath the black brushstrokes yet elsewhere sitting on top as spatters and drips—so that trying to ascertain the order the zones were painted in becomes impossible, an irresolvable paradox.

Indeed, this dribbly, loose, apparently sketchy style is crucial to the works’ argument. Heilmann often touches upon the history of geometric abstraction—through polygonal canvases recalling Ellsworth Kelly, color interactions after Josef Albers, and overt homages such as Little Mondrian (1985)—but she eschews hard-edge precision in favor of playfully wonky lines, paint that’s allowed to run joyfully free. Her architectural mode isn’t one of flush, finished perfection, then, but something more colloquial, handmade, precariously rickety—as if the scaffolding of color and form was only loosely held together, sometimes barely enough for the composition to qualify as a work of art. In that sense, she fits the Post-Minimalist, anti-form milieu that emerged in New York in the 1970s. Yet it’s interesting to note that she initially took up painting in response to the difficulties she faced, as a woman, in breaking into this mainly male-oriented scene. So there’s a gendered aspect to her style, too, a rejection of masculine rigidity and authority.

There’s also, perhaps, a rejection of ideas having to do with formalist autonomy, according to which an artwork should engage solely with the properties of its own medium. It’s questionable, after all, how much of Heilmann’s work is truly abstract. Early paintings such as Corona Borealis (1970) and The First Vent (1972), as their titles suggest, are surely representational—a tendency that returns in pieces from the past decade that feature recognizable images of road markings and crashing waves. Similarly, the ceramics she has continued making often toy with external referents and realism: Cup Drawing (1983) and Shadow Cup 2 (1985) are relief depictions, albeit abstracted to different degrees; Black Petal Plate (1983–84), meanwhile, really is a functioning plate. And the artist’s bright neon chairs, for all that their flat wooden planes riff on her painting practice, are certainly comfortable to sit in.

Heilmann’s slide projection Her Life (2006) unfortunately takes things a step too far. Combining a survey of her work with observational photographs—pairing a painting of jostling multicolored rectangles, say, with an aerial shot of parked cars—the piece draws connections that are too neat, too close to a kind of justification. Her paintings are gloriously, messily provocative and do not need to be explained so specifically.