"I met her at a party. And I danced with her, and that — that was it," he told Sunday Morning correspondent Sharon Alfonsi. "She's like an American beauty. She's got, you know, short nose, full mouth. Big, lots of teeth."
Many people say she is his muse.
"I would say that," Katz said. "Yeah. She inspired a lot of paintings. It's visual, you know. You see something you like and you want to paint it which is really simple."
Before Alex and Ada, there was just Alex. He was born and reared in New York City, an artist-in-the-making from boyhood.
"As a kid I was always painting everything," Katz said. "I put drawings all over the staircase when I was a kid. And my parents left them there for years and years."
Katz kept on painting, went to art school and painted some more. He came of age as an artist in the '60s, when abstract expressionism was all the vogue. But Katz clung to his own brand of realism.
"I had people screaming in galleries up until 1975," he said. "Screaming. Yeah. I had people scream that 'This is not art; this is crap.' 'He ought to go back to art school.' Stuff like that."
Ada remembers the very first time she sat for him.
"I'm aware of this man that I'm involved with in an extremely sensual situation," she said. "He's looking in my eyes. He's looking at my mouth…And it was not a sexy picture. I was fully dressed. I was freezing!"
First one, then another, then another — and now 40 of the portraits from this 50-year marriage of art and romance are on view at New York's Jewish Museum.
"One of the things he loves about painting Ada is that she gives him some distance. He doesn't have to sort of look into her soul," exhibit curator Ruth Beesch said.
"He's much more interested in style, appearance, fashion, in capturing a certain look. So he's interested in the way hair might flip on to the shoulder. He's interested in the kind of collar. He's interested in the way light breaks across a face and creates shapes and density. There's very little emotional attachment."
In fact, Katz' portraits of his wife seem so detached, so abstract, that he likens them to a mirror.
"That's what it's supposed to be," he said. "Yeah. It lets people see themselves. A lot of women think they're Ada."
None of his work is by mistake. Every stroke requires its own brush.
"Well, some brushes I use a lot," he said. "And some brushes I use once and never again, you know? Like this brush here — you use it on some night paintings where I wanted the white to spot. So I bought the brush [to dab] five times, ten times, clean it and that's it."
He is fanatical about color and says he sometimes spends more time mixing colors than painting the pictures. He says painting is like playing the piano. The actual work takes only a few hours. It took him less than a day to complete a 12-foot canvas.
With all his work, his wife remains his biggest focus. He has even multiplied her, but he still thinks his wife is one-of-a-kind.
"She's like a 10. In styling, you know?" he said. "Just her taste, taste is like — she really rarely makes a mistake," he said. "Ada can wear anything. If she thinks it looks right. It can be quite bizarre and be out of the five- and ten-cent store. Like she just took a tablecloth and wore it to a very fancy party. And someone said, 'Oh, who did that?'"
Although she has aged since he first began painting his wife, he says he paints what he sees.
"A lot of people don't know how old they are, you know? And she's one of them," Katz said. "She always thought she was about 10 or 20 years younger that what she actually is."