“Draw,” said the Exploding Head. Jack Alvarez, Georgia Hodges, Diane Richey-Ward and Andrei Wilenius already have; their works appear at Exploding Head Gallery, 924 12th Street, through January 28. It’s the most basic of all mediums: just paper and pencil or charcoal, a juxtaposition of light and dark. In “Stories of Friends,” Hodges weaves spider-web-fine lines of watercolor pencil on paper, with broader strokes like rivers meandering together in a frame shape, leaving a stark negative space at the center. Wilenius’ painstakingly realistic skull in “Selene 2005” serves as an upper female body. Although her head is tilted back in shadow, you can still barely make out her blissful countenance. With hair-fine graphite lines, Alvarez’s “Meeting Spring” offers a vision of teeming, emerging life and a critter with a head reminiscent of a pyramid, its all-seeing eye akin to ancient South American symbolism or the icon on the back of a dollar bill. For more information, call (916) 442-8424.