Robert Ryman's exploration of materials led him to utilize Plexiglas in a way that redefined the boundaries between painting and sculpture, further emphasizing his minimalist approach. In works such as the untitled piece from 1976, Ryman applied oil pastel to the textured and slightly translucent surface of sandblasted Plexiglas. This particular work, measuring 49 5/8 x 49 5/8 inches, demonstrates Ryman's commitment to exploring the "how" of painting—the physical object itself—rather than the "what"—the image, the story, or the symbolism traditionally conveyed by paintings​ (The Museum of Modern Art)​​ (www.wikiart.org)​.

The inclusion of square black oxide steel fasteners and hex bolts in this work not only secures the painting to the wall but also becomes an integral part of the artwork's aesthetic and conceptual framework. The visible fastenings, along with ruled pencil lines, expose the typically hidden mechanisms that attach paintings to walls, inviting viewers to contemplate the painting's construction and its relationship to space​ (The Museum of Modern Art)​. This innovative use of materials and fasteners exemplifies Ryman's interest in the essence of painting, focusing on the physical presence and materiality of the artwork rather than representational content​ (www.wikiart.org)​.

Ryman's works with Plexiglas contribute significantly to our understanding of his artistic practice, illustrating his belief in the importance of process, material, and the physicality of the artwork. Through these explorations, Ryman invites viewers to engage with the artwork on a deeper level, appreciating the subtleties of texture, light, and the interaction between the artwork and its environment.