Dr. Bob Shaffer says people accuse him of never finishing what he’s started. He sees it differently. “Only an artist knows when it’s done,” he says with his cool-green gaze. “When it’s done, it’s gone.”

In his workshop on Wilkinson Row in the French Quarter, he's taking Polaroid snapshots of a few paintings he's done in the last few days. One of them is the two-sided picture of "Working Manz Paradize,” a juke-joint in St. Joe, La., he used to frequent, its frame covered with antique Coca-C...