In July of 1963 the French artist Jean Dubuffet (1901–1985) declared of his radical lithographs, “Sometimes I took imprints of every chance element that might even suggest something: the ground, walls, stones, old suitcases, any or every sort of object—I even went so far as to do them from the naked skin of a friend’s back—and sometimes I obtained astonishing images…that I had sprinkled with tiny elements such as wires, crumbs, bits of torn paper, and all sorts of debris….” Dubuffet’s unconventional working process, described in his own words, is a significant theme in MoMA’s exhibition Jean Dubuffet: Soul of the Underground (on view through April 5, 2015). Evoking the texture and tactility of soil, water, stones, leaves, fog, and dew, the prints and drawings in the exhibition are also the focus of ongoing conservation and research within the Museum.

The first MoMA exhibition dedicated solely to Dubuffet in almost 30 years, Soul of the Underground presents nearly 100 examples of the artist’s work from the mid-1940s to the mid-1960s, emphasizing his extraordinary experimentation with natural materials and organic forms. In paintings, sculptures, drawings, and prints, Dubuffet often incorporated cut-up, collaged, and reconstituted elements from the natural world, stressing their physicality and building up densely suggestive layers of forms.

Two prime examples are the drawing Baptism of Fire (Baptême du feu) (1959), assembled from pasted leaves with oil on paper, and a group of three lithographs from 1953: Vegetation (Végétation), Branches with Birds (Feuillages à l’oiseau), and Landscape with Foliage (Paysage aux frondaisons), which were made by impressing leaves, ferns, and grasses to his printing surfaces. The processes he devised for these works on paper are similar to those he used in sculptures such as The Magician (Le Magicien) (1954), and in paintings such as My Cart, My Garden (Mon Char, mon jardin) (1955), in which he included grapevine roots, slag, and putty in the compositions, with the aid of common household items like kitchen sieves and rolling pins. Often obscuring the underlying base, Dubuffet’s integrative process of building layers by adding leaves, ferns, and grasses results in works that are like complex puzzles. Each new layer makes it more difficult to decipher the one beneath.

In the months leading up to the show, MoMA conservators and curators began analyzing the organic substances in these works to better understand Dubuffet’s use of unorthodox materials and techniques. However, it soon became apparent that we lacked the specific knowledge of foliage and vegetation necessary for such a project. As a result, we asked two botanists at the New York Botanical Garden—Daniel Atha and Marc Hachadourian—to assist us in identifying the species of leaves Dubuffet assembled in his 1950s works on paper.

On a rainy October morning, Atha and Hachadourian came to MoMA and worked with Erika Mosier, Conservator; Anny Aviram, Conservator; Laura Neufeld, Assistant Conservator; Jodi Hauptman, Senior Curator; Sarah Suzuki, Associate Curator; and Emily Cushman, Research Assistant, to decode Dubuffet’s curious choice of materials. Spending almost two hours together examining Baptism of Fire in the Paper Conservation Lab and Vegetation, Branches with Birds, and Landscape with Foliage in the galleries, we came to understand the astonishing diversity of elements that Dubuffet incorporated into his works. Collected during travels between his home in Paris and Vence, in the south of France, these included a tobacco leaf, a hart’s tongue fern, four different star-shaped seed pods, and, to our great amusement, the calyx (the green bottom stem) of a garden tomato (shown at left).

Dubuffet probably flattened the leaves—he may have used a rolling pin—before layering them messily atop one another in Baptism of Fire. Each leaf, once a distinct and independent form, now overlaps with the others, and together they produce an intricate composite image. While one leaf’s stem merges with the vein of a larger form, others remain intact and identifiable, such as the stark, parallel markings on the hart’s tongue fern.

In Vegetation, Branches with Birds, and Landscape with Foliage, the results were equally surprising. Dubuffet covered a variety of vegetal materials, including water lilies, ferns, and grasses, with ink and impressed them to his lithographic stones, which were subsequently printed on paper. The white-on-black forms in these botanical lithographs bring out the details in even the smallest leafy buds. With their chance effects and organic references, these works suggest an intimate connection with the ever-changing forces of nature.