SANTA MONICA

John Duff transforms concepts of slow movement--such as folding, billowing and twisting--into physical structures that have the authority of something tossed off by nature.

His cast fiberglass sculptures are hollow, translucent, awkward forms whose appeal is partly a matter of unpredictability. A view from one side rarely reveals the whole truth about a piece. The arc-shaped “Open Serrated Wedge” undulates smoothly enough with alternating open and closed passages, but most other works are complex orchestrations of curves and angles, broad expanses and cinched-up pockets.

Color is equally slippery; applied from the inside with long-handled brushes, liquid pigment bubbles along over rough surfaces, sometimes puddling up or splattering but never permeating thick, yellowish corners. And even the sculpture’s positions are difficult to pin down. All but one work--a red, yellow and blue spiraling form--are anchored to walls, but they project in such odd configurations that they might be floating.

You have to wonder where Duff comes up with these forms. They have a lumpy, organic look but manage to avoid associations--and to direct attention to themselves, leading viewers to discover painterly passages, luminous areas and langorously purposeful structure. In that respect this art conforms to a formalist credo, but form is no more an issue here than material and process. Duff has become identified with fiberglass, an industrial material, and he keeps no secrets about how he makes his sculpture. While earlier works clung to splinters from wooden molds, current ones retain vestiges of plaster.

Analysts can rest peacefully with the honest intelligence of his approach, while the experientially inclined immerse themselves in the presence of improbable structures. It isn’t easy to satisfy both camps, but Duff deftly does so. (BlumHelman, 916 Colorado Ave., to March 7.)