CITY OF GOD

The Met’ revelatory show on Siena.

- JACKSON ARN

Chop down a poplar tree. Other kinds of wood could work, too, but poplar is an especially soft one, and your task is to trim it into thin planes. These you'll need to coat in a barrier of plaster and animal gluenaked wood is highly absorbent, and you can't have it drinking down everything you put on it. Wait until the barrier has dried. Sand. Repeat until you have a perfectly smooth surface.

Sketch your preferred silhouettes with a stick of charcoal, slather the negative space in a gluey reddish mixture, cover that in translucent gold leaf (glueless, the metal has a queasy green tinge), and burnish that with a wolf's tooth. Now, and only now, you may pick up your brush.

The Met's new show about what happens next, "Siena: The Rise of Painting, 1300-1350," makes clear how astonishing it is that paint, of all things, became the center of Western art. Gold was prettier. Wood was tougher. Textile and ivory, both well represented here, travelled from city to city more freely. Nobody ever looked at an egg yolk, the signature ingredient in tempera, and thought "sublime," let alone "enduring," but here we are, seven centuries later. There may never be another big American exhibition about this freakish little era, when artists figured out how to make colorful ooze do their bidding.