''Black Sea'' is one of Milton Avery's most abstract paintings. Without its title, we would not know how to take it. Could it represent the flaming rim of the sun, so vast as to appear uncurved, against the airless blackness of galactic space? Or a cocked-head view of a golden plain with black clouds lowering distantly over a bright horizon? Or is it after all just an abstract painting whose point is to foil anecdotal interpretation? No. Any painting that combines simplicity and ambiguity as this one does, titled or not, cannot be intended to thwart our curiosity as to its meaning. On the contrary, this painting demands of us the imagination to see in it Avery's appreciation of abstraction as a technique of painting.
For Avery abstraction was a means rather than an end, a process of simplifying form whose aim is a universally legible visual vocabulary. In ''Black Sea,'' he has taken the subject matter traditional to marine painting and reduced it to three elements, or color areas, corresponding to ocean, surf, and sand. Another effort of abstraction is harder to notice: as in much of his mature work, Avery has eliminated the illusion of natural light from this ostensibly outdoor view. The only illumination that enters the picture is the incident light by which we view it. But it is also true that by eliminating illusions of light, Avery gives full play to whatever sensations of light the colors (such as the tawny yellow of the sand) may elicit on their own.
The removal of light and shade lends yet another ambiguity to ''Black Sea.'' Because there is no horizon line in the painting (or has its top edge become the horizon?), the black of the sea takes on a reminiscence of night sky, and we realize there is really no way to tell whether the picture is intended as a nocturne or a daytime view.
By smoothing away detail until his picture is nearly abstract, Avery brings the really mysterious aspect of the painting into plain sight. The mystery is in the way a stretch of flat, yellow ocher canvas can suddenly and recurrently suggest itself as a strand of ocean shoreline. Through simplifications of form and palette, Avery arrives at a picture that abstracts (distills) the fundamental but surprising fact that paint can appear to transmit visions.