De Niro and Admiral’s amiable separation corresponded with the couple’s first painterly success. In 1942 Admiral exhibited work at the Art of This Century Gallery and sold a painting to the Museum of Modern Art for a princely $100, way before any of her peers were accepted by the institution (Pollock sold his first canvas to MoMA two years later). De Niro Sr.’s debut solo show followed in 1946. And in the early ’50s, the fruits of his labors, bright French colors in the Hofmann style with thick, wavy brushstrokes, were shown at the Charles Egan Gallery alongside work by Willem de Kooning and Franz Kline.

"As a kid I remember I’d visit him at his studio," Robert De Niro now says of his father. "We weren’t living together, I was living with my mother, and it was nothing like his studio as you see it now. It was like a real studio, a total mess, and it stank of paint and turpentine." He describes his father as "affectionate ... always touching and hugging," and when he was growing up they’d see each other every few days, visit museums or go to movies, or just hang out in Washington Square Park. Once or twice his father would try to get him to pose for him, but De Niro says that he was a bad subject, unable to sit still.

His father was a loner; he lived, his son recalls, in "dank lofts ... at a time when nobody wanted to live in those areas. Often, he was the only tenant in the building." De Niro Sr. led an itinerant existence, moving from studio to studio around SoHo and the Lower East Side (one of these burned down in 1949, destroying a swath of his early work), and his son admits to having been embarrassed by him when he was young. "Most people I knew didn’t have ‘creative’ parents who lived in kind of grungy places and did odd jobs when they had to."

According to De Niro Sr.’s good friend, the painter Paul Resika, whom I met at his own studio on the Upper West Side (where Edward Hopper had once trained), back then De Niro "was the poorest of the poor," and totally committed to his work. An article written for Art News in the late 1950s depicts De Niro Sr. in one of his bare, paint-spattered studios, sitting on a mattress on the floor and contemplating a painting of a crucifixion. The subject absorbed him from 1953 to ’57, but always seemed to elude his perfectionist standards, and most of his canvases and numerous studies were rubbed out or destroyed. As the Art News writer put it, he seemed to make "slow progress against his own devils."

By that time, figurative expressionism was falling out of fashion. Abstract Expressionism and then Pop art ruled. De Niro Sr. never compromised his method to accommodate artistic fashion. The original artwork on the wall of his last studio spans four decades and is remarkably consistent. As Paul Resika puts it, De Niro Sr. found his way very young. "Even [Giorgi] Morandi changed more than Bob."

In the early ’60s De Niro left for France in disgust at his exclusion from the new commercial scene. He was prone to bouts of depression ("Since I was a child," De Niro Sr. once said, "I have felt in my heart two contradictory feelings, the horror of life and the ecstasy of life"), and one of his son’s biographers has De Niro Jr. bringing his father back to New York in 1965 after he suffered some kind of bipolar breakdown.

There are times during my interview with De Niro when I feel like Billy Crystal’s character in Analyze This, prodding him for oedipal information about his father. When I bring up the question of the artist’s depression he clams up: "I don’t know enough about it, he wouldn’t tell me. He wouldn’t share that with me. I heard a little about that, yeah, but I’m not sure — it’s very possible." One of De Niro Sr.’s friends described him as "a lonely soul" with an "elegant mind."

In the late ’60s and ’70s, De Niro Sr. exhibited at regular intervals, but his early success was never repeated, and he taught at Cooper Union, the School of Visual Arts, and the University of Buffalo to make ends meet. "De Niro is trapped on the dark side of the success machine," one art critic observed in an article that juxtaposed Warhol’s "glittering career" with "the aristocratic artist" De Niro, whose "passionate works aim for elevated levels of historical discourse." His son remembers how his father detested dealers, whom he considered to be parasites, and recalls how one gallerist gave his father a gift of a cardboard box of dried soup. "That’s what they gave him for Christmas — and it wasn’t even wrapped!"