Glorious Gainsborough

For a portrait painter, the ability to get along with his sitters is crucial—after all, the client pays the bill—but the exercise can be wearing. Possessing a volatile disposition, Thomas Gainsborough often felt exasperated with “the nature of my damn’d business”: when an effete alderman in Bath, wearing his “five guinea new powdered bob wig,” kept insisting on being issued with a more prominent dimple, “Gainsborough burst forth in laughter, threw his pencil upon the ground, and said: ‘D—m the dimple in your chin, I can neither paint that nor your chin neither.’ ”

But others were too powerful to be handled this way: that was the case with the Earl and Countess of Dartmouth, who had insisted that Lady Dartmouth wear a classical outfit in her portrait, and Gainsborough had reluctantly gone along. Unlike Sir Joshua...