Wendy Artin’s life-size watercolor interpretations of the Elgin Marbles are such extraordinary technical feats that my initial reaction to them, as a lesser practitioner of the medium, was gut-sinking envy. Typically, for this degree of realism, one would begin with a preparatory sketch in pencil. Artin dives in with watercolor on damp paper, corralling pools of pigment with a brush and a rag until they give her the shape she wants. If you’re unfamiliar with the materials, imagine trying to draw a portrait with orange juice spilled on a kitchen counter.