When Donald Judd first saw one of Dan Flavin's neon tubes "placed at a diagonal on an approximately eleven by eleven wall" on exhibition in 1964, he complimented Flavin by declaring that this work made "an intelligible idea of the whole wall". In many ways Judd's sculptural vertical progressions - the "Stacks" as they have come to be known - do exactly the same thing. Separating the space from floor to ceiling into a sequence of solid versus empty form and open versus enclosed space, the "Stacks" articulate the real space of the room with an unprecedented degree of simplicity and precision.
"It isn't necessary for a work to have a lot of things to look at, to compare, to analyse one by one, to contemplate", Judd had written in his seminal essay Specific Objects in 1965. "The thing as a whole, is what is interesting. The main things are alone and are more intense, clear and powerful." For this reason Judd's "Stacks" - which the artist first began to develop in 1966 - are widely regarded as being Judd's "breakthrough" works: for in them he developed for the first time, the simple and elegant mathematical language that would characterise and define all his subsequent work.
Judd believed that the thing itself was what was important in a work and that nothing should detract from the work's representation of itself. Towards this end he was one of the first artists to insist on having all his works made by industrial means and to use only cold impersonal industrial materials. Only in this way, he believed, could he achieve the absolute precision necessary for his work to be seen only for what it was and not for the craftsmanship or means by which it had been made. Similarly a simplicity of form was required in order to explain his ideas in the most direct and non-elaborate way. The open box became the perfect structure for Judd, in that it intersected in the simplest way, all sculptural notions of space, by being simultaneously both an enclosed and an open form.
The box suited Judd because the "image, all of the parts, and the whole shape are co-extensive" Judd declared, and consequently no hierarchy is involved in its formal properties. Through his progressions, - which consist of a precisely-measured and sometimes mathematical sequence of open and closed three-dimensional form - Judd extended the non-hierarchical formal properties of the rectangular box from the floor to the wall and more importantly, into the real space of the viewer. The "Stacks" are the fullest and simplest realization of this principle being a clearly identifiable whole that is made up of separate, independent and equal parts.
Representing the culmination of his artistic development in the 1960s, Judd's "Stacks" also stand at the crossroads of his art, for as a work like Untitled of 1969 elegantly shows, through the simplest of means and with the most impersonal of materials, Judd was able in these works to create a powerful sense of ethereal transcendence - something Robert Smithson at the time described as an "uncanny materiality".
Rising from the floor, the ascendant progression of copper rectangles in Untitled generates a sense of penetrating and being penetrated by space. At the same time however, the rich colors and the precision of the work's construction provokes a sense of lightness that combines with this inter-penetration of space to lend the work an aura of the mystic. Though evidently not the case, the mechanical precision of this intersection of solid and void is so clearly a product of the rational human mind that it seems to exist outside the real physical space of the viewer. Indeed it appears as if the work exists on the borders of a space/time continuum. This sense of his work invoking the mystic was however, firmly rejected by Judd in the same way that he rejected Smithson's notion of "uncanny materiality", but it is nevertheless an aura that many of his finest works attain.
For Judd, Smithson's sense of "uncanny materiality" was merely the mystery of what he termed the "invisible" elements of art. "Material, space and color are the main aspects of visual art," Judd wrote. "Everyone knows that there is material that can be picked up and sold but no-one sees space and colour. Two of the main aspects of art are invisible, the basic nature of art is invisible." Unlike many of Judd's later works that increasingly employed artificial colour as a subversive element, Untitled employs the innate color inherent within the material from which it has been made to celebrate this union of material, space and color. United by the conformity of the single material from which it has been made - (copper - the most richly colored of all the inexpensive metals) - Untitled is also divided by the myriad light effects that the highly polished surface of the metal produces. The infinite is here contained through color within the unit and the unit is a separate but equivalent part of a material progression. This progression in turn is an articulation of the space within it and around it. In this way, and by using only the simplest of means, Untitled forms a marriage between material space and colour and reveals itself to be the physical summation of Judd's highly ideological aesthetic.