Stephen Kaltenbach’s work is about time: how it changes everything, how insights take shape over a lifetime, how identity evolves slowly, how values shift, or deepen, or both. He made this interest literal by creating many time capsules over his career: sealed metal receptacles etched with titles and dates on which to open them. It is unknown what, if anything, is inside Kaltenbach’s capsules, as none have ever been opened. However, it is historically the practice of such endeavors to include ephemera from the time they were created that would, the maker assumes, be of interest and probably otherwise be lost over the intervening time. Thus it is very appropriate that his retrospective exhibition, titled The Beginning and The End, co-curated by Constance Lewallen and Ted Mann, is itself a kind of time capsule, heavily weighted toward his neglected early work of 1967-70, and then “opened” with a smaller coda of a gallery featuring his often-masterful output in the ensuing decades.

Another moving aspect of this exhibition is that it takes place at the Jan Shrem and Maria Manetti Shrem Museum of Art, University of California, Davis campus where Kaltenbach was a student some six decades ago (at the same time as his contemporary Bruce Nauman). Both artists found almost immediate acclaim within a very short time of leaving school as early masters of conceptual practice. Kaltenbach had moved to New York and was so successful that he had a one-person exhibition curated by the great Marcia Tucker at the Whitney Museum within three years. However, Kaltenbach fell victim to the excesses of the fast lane in New York and in order to save his life, returned to California, became a born-again Christian, and taught art in relative anonymity at a public university until his retirement around 2010.

Kaltenbach’s breakthrough early idea was to place text pieces disguised as ads in Artforum magazine. Twelve of these are on display, both his small ad and, for context, the cover of the issue. Text was always a central part of conceptual practice (notably Lawrence Weiner and Joseph Kosuth in New York and his teachers at UC Davis, William T. Wiley and Robert Arneson). Kaltenbach’s ads are generally instructions or advice, such as “Become a Legend ” or “Build a Reputation.” They’re like updates of Yoko Ono’s 1964 book of suggested actions, Grapefruit, with the theatrics excised. They were the first inkling of artists’ realizations that they could coopt mass media and put it to use distributing their work.

Architecture—both as a form of sculpture and as social construct—is another theme of the artist’s body of work. Drawings and proposals for inaccessible rooms in museums and galleries appear frequently. Such rooms were meant to be occupied by Kaltenbach, but like the time capsules, we’d never know what was truly inside. He also installed painted wall works, (one of which is recreated for the exhibition) in which a slightly altered shade of gray from the institutional paint job might affect the visitor’s experience of a room without consciously being aware of the intervention. His short texts on brass plaques, which are only complete when embedded in public sidewalks, are meant to be eroded by pedestrians, a kind of time-based public art about the architecture of walking. It has been imitated in countless forms of urban art around the United States.

Kaltenbach was invited to participate in several large international exhibitions, including the legendary When Attitude Becomes Form, curated by Harold Szeemann. Kaltenbach sent a rubber stamp of red lips to be hand-stamped, graffiti-style, on walls in the museum and around town. In others he agreed to participate in the exhibition but deliberately never sent any art object, which was his contribution. He was interested in the same question: if his contribution to the show is not visible, is it like his  probably-empty time capsules, or his possibly occupied rooms? Can work be hidden, partial, non-existent, or withheld and still be art?

The final room of the exhibition contains highlights of Kaltenbach’s post-New York production. It is dominated by three large, extraordinary paintings that each, in different ways, are meditations on time, transcendence, and mortality. Now in his 80^th year, Kaltenbach is clearly thinking about the end of life, sometimes more successfully than others. In Sunset, a straightforward rendering of a blazing fluorescent-colored dusk, seen through the filter of a forest, is problematized by a tricky surface. Dozens of round, three-dimensional, stepped weather-map-like shapes ripple across the surface. The effect is an embodiment of the psychedelic experience as sacred landscape. International Harvester creates a monument to a common experience of lonely nighttime highway driving, in this case an ephemeral moment when a passing truck evokes deep, inchoate emotions. The third painting is Kaltenbach’s masterpiece, Portrait of My Father. I have literally never met anyone who has seen this object and not considered it one of the greatest paintings of the twentieth century. It depicts a highly realistic, very old man’s head, in repose, and overlain with an abstract, transparent pattern based on Islamic arabesques. The entire image is poised to completely merge into light; it is a breathtaking event in paint that depicts human grace. A pithy medical definition of dying goes: stop eating, stop drinking, stop breathing. Kaltenbach’s version of this somber litany ends the show with a time capsule-like triptych with the titles, Last Act, Last Word, and Last Thought.

Kaltenbach’s increasing acknowledgement for his major contributions to conceptual practice will surely be augmented by this still-powerful exhibition. His post-1970 career is as though by an entirely other artist, one whose meditations on mortality and our relation to the cosmos could not be more different, and at its best, be just as impressive.