In 1990, Clement Greenberg, the influential formalist art critic stated: "Dan Christensen is one of the painters on whom the course of American art depends."

For multiple reasons, particularly the fading away of formalism, which emphasized painting's two-dimensional nature as an object in and of itself, Christensen didn't reach the lofty heights that Greenberg predicted.

But that doesn't mean he couldn't paint or that his continually evolving abstraction doesn't continue to vibrate with brilliant colors, variations in line and, in his later works, an explosive freedom.

"Dan Christensen: Forty Years of Painting," a retrospective exhibition featuring more than 30 of Christensen's most important works, was appropriately organized jointly by Kansas City's Kemper Museum of Contemporary Art and the Sheldon Museum of Art, where it is on view through Jan. 31, 2010.

Christensen, who died suddenly at age 64 in 2007, was born in Cozad, attended high school in North Platte and started college in Chadron before transferring to the Kansas City Art Institute, where he graduated in 1964. His is a biography that makes the retrospective a natural for the two institutions.

Working primarily in New York, Christensen was long associated with the color field movement, which Greenberg championed. But his work extended beyond color field's thinly painted or stained canvas and the removal of abstract expressionist gestural brushwork and any hint at depth from the surface.

While a brush isn't present in the work, the soft-edged, spray-painted lines that dance across the 6-by- 10 "Mallee" and the 9.5-by- 14.5 "Serpens," both from 1968, reveal the artist's hand, making the latter a joyous study in color, with yellow, green, pink and light blue snaking above fields of darker blue and orange.

Similarly stepping away from color field, "Kifwele Memory" (1984) is covered with thick silver and yellow ochre acrylic paint with angry scrapes of lines cascading across the painting.

In Kansas City, the exhibition was hung chronologically in the large, roundish temporary exhibition gallery. That traditional hanging provided a strong sense of Christensen's development, a continual exploration of line, color and technique that, as curator/critic Karen Wilkin points out in the exhibition's catalog, made him a "painter's painter."

At Sheldon, "Dan Christensen: Forty Years of Painting" is hung by image/shape in the Philip Johnson building's very formal white cube galleries - one for loops and lines, one for harder-edged work and one dominated by circular patterns.

The connections between the paintings then become both chronological/developmental and aesthetic, showing how Christensen, to some degree, moved back and forth between abstract styles over the decades.

For example, 1967's "Conjugate," one of the earliest paintings in the show, is covered with soft-edged, sprayed loops of muted yellows and greens. Next to it is 2005's "Rhymewriter #7 - White," in which the loops break free, become intertwined rather than stacked, take on hard edges and startle with bright primary colors.

"Rhymewriter #7 - White" is one of the paintings that most vividly conveys Christensen's late career explosion of freedom, a sense that also comes through in the rolling hoops of "Yellathrilla," a 2006 piece that is the most recent work in the show.

That freedom is an indicator of a mature painter turning loose his considerable skills and worrying not about where or how the work will be classified. That period seems to begin early in paintings like "Ray," a 1999 set of concentric, but far from tight circles that starts with a glowing white, sprayed interior circle around what Christensen called a "spot," which is eventually surrounded by a large, dripping, gestural unbalanced ring.

Taking on a grid and splatters in "Class Trip" (2000) and exploring the unbounded line in pieces like "Coach" (2003), Christensen's late work has an exuberance and grip lacking in his early paintings and makes one wonder what he might have done, for his best work is his latest.

It remains to be seen how exactly Christensen will be regarded in art history - his work is well enough known and in enough museums that he'll certainly be noted. But for now, it is clear that he was a superb painter with a great sense of color and an exploratory sense of line.

That makes "Dan Christensen: Forty Years of Painting" a valuable exhibition and the best show at Sheldon in 2009.

A final note: Sheldon's temporary exhibition galleries were not large enough to hang all of the paintings in the show. Two paintings are hung on the walls of the Great Hall, and others are not on view.

It also was difficult to get the larger works in and out of the museum, which was constructed in the early 1960s, because of the size of the crates in which the paintings were shipped. The need to display properly and handle large-scale contemporary art is one of the driving reasons for the planned Sheldon expansion in the Haymarket.

Reach L. Kent Wolgamott at 473-7244 or kwolgamott@journalstar.com.