Newman proclaimed Onement, I to be his artistic breakthrough, giving the work an importance belied by its modest size. This is the first time the artist used a vertical band to define the spatial structure of his work. This band, later dubbed a "zip," became Newman's signature mark. The artist applied the light cadmium red zip atop a strip of masking tape with a palette knife. This thick, irregular band on the smooth field of Indian Red simultaneously divides and unites the composition.
Gallery label from 2006.
Characterizing Onement, I as “the beginning of my present life,” Newman discovered in this breakthrough work a wealth of visual and conceptual complexity. He began by staining a modestly sized canvas with crimson. Over this richly hued ground, he applied a strip of masking tape, and then used a palette knife to scumble over it with cadmium orange. He had originally intended to remove the tape, leaving a lighter strip edged by orange flickers. Instead, he recognized in the vertical line it formed—which he would call a “zip”—a visual device that distilled painting to its essential qualities of space, color, and figure-ground relationship. Newman would spend the rest of his career exploring the potent possibilities of zips on fields of color, creating compositions whose purpose he described in lofty terms: “The image we produce is the self-evident one of revelation…that can be understood by anyone who will look at it without the nostalgic glasses of history.”
Additional text from In The Studio: Postwar Abstract Painting online course, Coursera, 2017