As a child, Alexandra "Alex" Tolstoy created oil sketches of Rembrandts and of angels in Michelangelo paintings. "I started with something easy," Dr. Tolstoy, BA '68, MA '72, jokes of the latter.

But at age 9 she hung up her brushes after deciding to focus on science. She had always planned to return to art, and she did—at 60 years old. A few years later, after retiring in 2012 from a career in ocean acoustics, which built upon her doctoral work in applied math, Dr. Tolstoy began to devote even more time to her art.

Starting again was a challenge. "As a kid, you just throw stuff out there, and it works," she says. And she didn't make it any easier by shifting to watercolors, a notoriously unforgiving medium in which colors can quickly get muddied.

Dr. Tolstoy's technique might best be described as the Zen of watercolor. She talks of "letting the watercolor do all the work," and being "free" and "standing back" from the materials. (Aficionados will want to know: She uses Arches paper, and Winsor & Newton paint—because it "granulates"—or sometimes gouache.)

Although she does wonder what her work would be like if she hadn't taken a 51-yearhiatus, she says, "I'm glad I did science." And she brings to painting a scientist's curiosity and appreciation of results that can't always be predicted.

"I tend to think of oil painting like chess. You make a move; there's no randomness involved. It's very cerebral, and that's wonderful, but there's a flipside," she says. "If you play backgammon, you've got to throw the dice and you don't really know what you're going to get. To some extent, watercolor is like that. You have this sky that's going on, but there's a real element of randomness. And that, to me, makes it so much more interesting."

Dr. Tolstoy's art will appear in a solo exhibit at the Torpedo Factory in Alexandria, Va., in June 2016. To learn more about the artist, visit atolstoyart.com.