There is precious little work by Pop icon Andy Warhol that hasn’t already been exhibited, analyzed, and probably emblazoned on a t-shirt. But one of the few aspects of the late artist’s work that’s been rarely seen by the public is the tremendous cache of photographic contact sheets he accumulated between 1976 and 1987, a period when he was in the habit of maintaining a daily visual diary of photos.

In 2014, the Andy Warhol Foundation chose Stanford University’s Cantor Arts Center to receive this collection: 3,600 contact sheets containing 130,000 exposures. In return for the trove, the Cantor Center’s archivist spent three years digitizing the material, and a selection is now on view in a revelatory show co-curated by professors Peggy Phelan and Richard Meyer, “Contact Warhol: Photography Without End.”

Warhol’s 35-millimeter camera was a continual presence in his life, and he often shot close to a roll of film per day. In the extensive array of black and white negatives on view in “Contact Warhol,” one can see the stages of his decision-making process: Some frames are struck through with an X, others are highlighted in a waxy red crayon to delineate his final selections. Unlike many of the Warhol paintings that hit the auction block or headline a museum collection, these contact sheets bear the rare mark of the artist’s own hand.

As part of the gift, the Cantor Center has the right to select, enlarge, and print images from the contact sheets, which Warhol didn’t intend to have published—a notion the curators grapple with in the impressive exhibition catalogue. The images include Bianca Jagger shaving her armpits, Keith Haring posing with his boyfriend, plus shots of Liza Minnelli, Jean-Michel Basquiat, Nancy Reagan, and many others.

Appearing alongside Warhol’s negatives are the finished silk screen paintings that resulted, many loaned from the Warhol Museum for the exhibition.

“These contact sheets comprise Warhol’s last major body of work, largely unseen until now, some thirty years after his death,” Peggy Phelan writes in the catalogue. “These past three decades might be seen as a kind of developing ink, as if the exposures were slumbering in a very slow chemical bath, and the conditions of visibility did not allow us to see them until now.”

See images from “Contact Warhol: Photography Without End” below. The exhibition is open at Stanford University’s Cantor Arts Center through January 6, 2019.