A Los Angeles native, Peter Alexander studied architecture and worked briefly for modernist émigré architect Richard Neutra before studying art. He began experimenting with cast resin in 1964—based on experiences repairing his surfboard with liquid resin—and his artistic breakthrough occurred soon after, following the debut of his small, wedge-shaped, cast resin sculptures.

Untitled belongs to this pivotal series of works and is an early example of California Light and Space art. In order to create the wedge-shaped works, Alexander set a long trough on top of a table elevated on one end and then poured liquid resin from that end. As a result of this process, the resin became most concentrated at the center of the work, while the outer, particularly upright, edges remained relatively transparent. Once called “containers of silence, as if one were underwater” by a contemporary critic, these cast resin sculptures invite wonder with their subtle gradations of color, obfuscation of hardness and softness, and the ability to simultaneously exude warmth and coolness. Citing the toxicity of the material, Alexander would stop working with polyester resin in 1972 for at least several decades.