An iconic form in Donald Judd's oeuvre, Untitled (Bernstein 89-1) is a steel and colored Plexiglas stack executed in 1989, one year after the artist's celebrated retrospective curated by Barbara Haskell at the Whitney Museum of American Art, New York. Judd conceived the stack as one of the more elegant solutions to his concepts concerning space, form and color as outlined in his seminal treatise, 'The Specific Object', published in 1965. Judd's stacks are vertical objects consisting of single units, each with identical dimensions hung one above the other on a wall and interspersed with negative space of equal size. Proportion is an essential criterion in Judd's aesthetic and the ratio of positive to negative space within the construction of the stack is fundamental in its ability to operate as a cohesive whole. Disregarding any hierarchical use of form, here Judd focused on creating compositional harmony through a sequence of equal subordinate parts. Indeed, the interplay of positive and negative space in the work, both of equal importance in Judd's ultimate composition, implies an infinite series by denying a base or summit. Standing ethereally in its own space, Judd's stack punctuates space, assuming a panoramic splendor. Of this desire to present a harmonious object Judd explained, "I'm strongly against any division of thought and feeling, which I think is a completely wrong division. So, when you start dividing it up and talking about it then I don't know how to deal with it.I think it's much exaggerated in its use and rather dangerous in its use" (D. Judd, quoted in J. Poetter, 'Back to Clarity: Interview with Donald Judd, 1989', in Donald Judd, exh. cat., Staatliche Kunsthalle Baden-Baden, 1989 p. 91).
The stack became a motif to which Judd returned often throughout his career, a form that evidently allowed him to explore how different combinations of color and materiality could inform his spatial concepts. In its juxtaposition of rigid form and transparency, Plexiglas blurs the line between the positive space of Judd's objects and the negative space interspersed in between. Indeed the transparent quality of Plexiglas informs the material object as well as the negative space through its emission of an ethereal glow. Plexiglas was a material that held special resonance for the artist in its ability to embody a multitude of industrial-grade colors. Judd turned to the newly invented Plexiglas for its spotless luminosity and clear-cut sharpness and for its ability to transmit color without betraying its mode of manufacture. More so than any other material in Judd's repertoire, because of its ability to become any color and any degree of transparency and opacity, Plexiglas lived up to the artist's stipulation that material and color should form a single entity, making it a favored material to combine with different metals in his stacks. Preferring to leave the surfaces of his materials unaltered in an effort to present something of their indelible nature, Plexiglas offered Judd a most effective way to do this, by presenting a colored material that is free of any trace of manual intervention. As explained by Judd, "the piece should never be, as in Abstract Expressionism, a spectacle of its making; it should just be there" (D. Judd, quoted in Donald Judd, exh. cat., Pace Wildenstein, New York, 2004, p. 8). Visually activating the space between and around the stack with diffused spectral light, Judd achieves a sort of secular transcendental splendor much like Gerhard Richter's stained glass window made for Cologne cathedral. In the streamlined form of Untitled, the rigid outline of the stacked translucent green panes multiplies beyond its cubic parameters, presenting visual contradictions in its very materiality. In so doing, the quality of transparency imbues the work with a potent sense of illusionism. Of this phenomenon Judd notes: "the illusionism is real-a physical consequence of the structure of the work, not depicted or suggested as in painting" (D. Judd, quoted in W.C. Agee, 'Unit, Series, Site: A Judd Lexicon', Art in America, vol. 63, no. 3, May-June 1975, p. 46).
Recalling Brancusi, whose Endless Column investigated the notion of objects in space, an overriding interest for Judd was the way in which different materials could work in polarity or alliance to create a unified whole. Indeed Judd stated, 'the greater the polarity of the elements in a work, the greater the work's comprehension of space, time and existence" (D. Judd, John Chamberlain: New Sculpture, New York, Pace Gallery, 1989, pp. ix-x). Composed of two seemingly antithetical materials, Untitled would at first seem to go against Judd's statement in 'Specific Objects' that his work be viewed as '[a] thing as a whole' rather than a conglomeration of parts. The juxtaposition of steel and Plexiglas in Untitled augment the strategies already present in Judd's stack concept, of crating harmonies through material and sensory polarities. Playing with the distinction between definite and indefinite qualities of visibility, this stack seems to defy gravity. Through the interaction between the softly glowing color of the Plexiglas coupled with the cool steel, Untitled takes on the characteristics of light filtered through cascading water, an amorphousness that would seem at odds with its rigid makeup. Of this Judd explained, "[there is a] three-way polarity of appearance and meaning, successive states of the same form and material. A piece may appear neutral, just junk, casually objective; or redundant, voluminous beyond its structure, obscured by other chances and possibilities; or simply expressive, through its structure and details and oblique imagery" (D. Judd, 'Specific Objects', Arts Yearbook 8, 1965, p. 82).