In the late 1940s, Donald Judd began to practice as a painter. His first solo exhibition, of expressionist paintings, opened in New York in 1957. From the mid-1950s to 1961, as he explored the medium of the woodcut, Judd progressively moved from figurative to increasingly abstract imagery, first carving organic rounded shapes, then moving on to the painstaking craftsmanship of straight lines and angles. His artistic style soon moved away from illusory media and embraced constructions in which materiality was central to the work. He would not have another one person show until the Green Gallery in 1963, an exhibition of works that he finally thought worthy of showing.
By 1963 Judd had established an essential vocabulary of forms — ‘stacks’, ‘boxes’ and ‘progressions’ — which preoccupied him for the next thirty years.Most of his output was in freestanding "specific objects" (the name of his seminal essay of 1965 published in Arts Yearbook 8, 1965), that used simple, often repeated forms to explore space and the use of space. Humble materials such as metals, industrial plywood, concrete and color-impregnated Plexiglasbecame staples of his career. Judd's first floor box structure was made in 1964, and his first floor box using Plexiglas followed one year later. Also by 1964, he began work on wall-mounted sculptures, and first developed the curved progression format of these works in 1964 as a development from his work on an untitled floor piece that set a hollow pipe into a solid wooden block. While Judd executed early works himself (in collaboration with his father, Roy Judd), in 1964 he began delegating fabrication to professional artisans and manufacturers (such as the industrial manufacturers Bernstein Brothers) based on his drawings. In 1965, Judd created his first stack, an arrangement of identical iron units stretching from floor to ceiling.
As he abandoned painting for sculpture in the early 1960s, he wrote the manifesto-like essay “Specific Objects” in 1964. In his essay, Judd found a starting point for a new territory for American art, and a simultaneous rejection of residual inherited European artistic values, these values being illusion and represented space, as opposed to real space. He pointed to evidence of this development in the works of an array of artists active in New York at the time, including Lucas Samaras, John Chamberlain, Jasper Johns, Dan Flavin, George Earl Ortman and Lee Bontecou. The works that Judd had fabricated inhabited a space not then comfortably classifiable as either painting or sculpture and in fact he refused to call them sculpture, pointing out that they were not sculpted but made by small fabricators using industrial processes. That the categorical identity of such objects was itself in question, and that they avoided easy association with well-worn and over-familiar conventions, was a part of their value for Judd. He displayed two pieces in the seminal 1966 exhibit, "Primary Structures" at the Jewish Museum in New York where, during a panel discussion of the work, he challenged Mark di Suvero's assertion that real artists make their own art. He replied that methods should not matter as long as the results create art; a groundbreaking concept in the accepted creation process. In 1968, the Whitney Museum of American Art staged a retrospective of his work which included none of his early paintings.
In 1968, Judd bought a five-story building in New York that allowed him to start placing his work in a more permanent manner than was possible in gallery or museum shows. This would later lead him to push for permanent installations for his work and that of others, as he believed that temporary exhibitions, being designed by curators for the public, placed the art itself in the background, ultimately degrading it due to incompetency or incomprehension. This would become a major preoccupation as the idea of permanent installation grew in importance and his distaste for the art world grew in equal proportion.
Judd started using unpainted plywood in the early 1970s, a material the artist embraced for its durable structural qualities, which enabled him to expand the size of his works while avoiding the problem of bending or buckling. Plywood had been the staple of his art earlier, but never unpainted. He later began using Cor-ten steel in the 1980s for a small number of large-scale outdoor pieces, and by 1989 would create single and multi-part works with the material. The Cor-ten works are unique in that they are the only works the artist fabricated in Marfa. The artist began working with enamel on aluminum in 1984, when he commissioned Lehni AG in Switzerland to construct works by bending and riveting thin sheets of the material, a process Judd previously used to create furniture. These pieces were initially created for a temporary outdoor exhibition in Merian Park outside Basel. Judd would continue to produce pieces using these techniques through the early 1990s. Judd’s work with enamel on aluminum greatly expanded his palette of colors, which had previously been restricted to the colors of anodized metal and Plexiglas, and led to the use of more than two colors in an individual artwork. Combining a wide range of colors, he used the material to create five large-scale floor pieces and many horizontal wall works in unique variations of color and size. Judd’s only known work in granite, an untitled Sierra White granite floor piece from 1978, measures 49 x 98 x 98". The structure is composed of two vertical slabs that rest on the floor, to which the bottom component is conjoined, and the ceiling of the structure extends to the outer edges of the vertical walls.In the early 1970s, Judd's art increased in scale and complexity. He started making room sized installations that made the spaces themselves his playground and the viewing of his art a visceral, physical experience. Throughout the 1970s and 1980s he produced radical work that eschewed the classical European ideals of representational sculpture. Judd believed that art should not represent anything, that it should unequivocally stand on its own and simply exist. His aesthetic followed his own strict rules against illusion and falsity, producing work that was clear, strong and definite. Supported by a grant from the National Endowment for the Arts, Northern Kentucky University commissioned Judd with a 9 feet (2.7 m) aluminium sculpture that was unveiled in the middle of the school's campus in 1976. Another commission, Untitled (1984), a three-part sculpture out of concrete with steel reinforcements, was installed at Laumeier Sculpture Park.