"THIS WINE IS PERFECT for sipping in a wine bar," says Clément Pinard, pointing at a glass of his Sancerre Rouge. "Perhaps while you are waiting for your girlfriend," he adds. "With a small light hanging down from above."

It's an attractive mental picture but I think Mr. Pinard, who runs Sancerre's Domaine Pinard with his brother, Florent, may be getting a little carried away, so I look at my glass and take a sniff. The red wine is slightly pale—if I hold it up to the light I can see through...