Stored away between the paintings and sculptures in MoMA’s storage facility lay a forgotten treasure from the Museum’s past: 11 disassembled pieces of the original stretcher from a Pablo Picasso masterpiece. Museum registrars rediscovered the group of stretcher bars during routine organization earlier this year, and since stretchers are occasionally replaced to ensure that a canvas is adequately supported, the discovery did not immediately strike them as significant. However, the large size and design of the parts of one stretcher were very unusual. With almost no identifying information, save for an old, torn sticker that included Picasso’s name, the stretcher was brought to the attention of longtime MoMA painting conservator Anny Aviram. To her mind there was only one painting that could possibly fit: Picasso’s massive antiwar mural Guernica, which had spent 42 years at the Museum on extended loan from the artist.

The famed painting is widely recognized as one of the 20th century’s greatest works of protest art. Created for the Spanish Republic’s pavilion at the 1937 Paris International Exposition of Art and Technology in Modern Life, or the World’s Fair, for short, Guernica measures an enormous 11.5 feet tall by 25.5 feet long (349.3 x 776.6 cm). Picasso received the commission to paint a mural in January 1937; although he had lived in France since 1904, he was keenly aware of the civil war that raged in his native Spain between the Republic and General Francisco Franco’s Nationalists. Picasso initially had difficulty finding inspiration for the work’s subject; early sketches show he had explored apolitical scenes of an artist’s studio. Then, on April 27, 1937, German warplanes, at the service of Franco, bombed the Republican-controlled Basque town of Guernica, killing innocent civilians and decimating the town. When news of the massacre reached Paris, Picasso set out to depict the atrocities for the world to see.

The attack on Guernica occurred just weeks before the Exposition’s May 25 opening, and it would take Picasso until June to finish the mural. The custom-made stretcher, however, was likely built much earlier, soon after he received the commission. To support such a large canvas, it was important to have a strong, sturdy stretcher. Using thick, heavy wood, each piece was hand-carved to create interlocking joints where crossbars—five vertical and two horizontal—intersected, while a peg-and-hole system connected crossbars to the exterior supports. Most importantly, a diagonal joint was used to connect two pieces of wood to create each 25.5-foot-long horizontal support, an unusual design for a stretcher.

This diagonal joint was one of a few clues confirming Aviram’s hunch that the 11 pieces discovered in storage did indeed once support Guernica. Another important clue was the aforementioned sticker, which turned out to be a paper label used to identify incoming loans to an exhibition. Still legible on the label are “San Francisco Museum of Art” (now SFMOMA) and “Picasso.” The word “mural” is written in for the title (this was often used to refer the work before Guernica was made its definitive title), leaving little doubt about the stretcher’s origins.

The disassembled stretcher was brought from storage to the Museum, where frame shop foreman Peter Perez attempted to fit the pieces together. Yet Perez concluded that the dimensions didn’t match up; the stretcher was much too small to be Guernica’s. Stumped, Aviram consulted a fellow conservator during a trip to the Reina Sofia, the Madrid museum where Guernica is currently on display. They agreed that no other painting could belong to the stretcher, so when Aviram returned to New York she had the 11 heavy stretcher bars brought to MoMA’s conservation studio for a second examination.

The pieces were laid out on the floor of the studio and arranged according to various markings for assembly. It quickly became apparent that some pieces were missing. Conservation fellow Ellen Davis then created a diagram of the stretcher, showing the pieces they had and those that, given the design, must be missing. The dimensions of this reconstructed stretcher matched those of Guernica exactly. Documents in the conservation file revealed that Guernica’s original stretcher had been replaced in 1964—it was too heavy and worn to properly support the enormous canvas—confirming that what was uncovered in storage was the original stretcher. To find out where the stretcher had been, both before and after 1964, I went digging in the MoMA Archives.

Despite receiving mixed reviews at the Paris Exposition, Guernica quickly became a universal symbol of the inhumanity of modern war in an increasingly tense Europe. Following the close of the Exposition at the end of 1937, the painting toured Europe (notably, it did not travel to Spain) and then the United States, where it was displayed across the country to raise money for the Spanish Refugee Relief Campaign. On Monday, May 1, 1939, Guernica arrived in New York for display in the Valentine Gallery. It then traveled to Los Angeles, San Francisco, and Chicago before returning to New York on October 16, 1939, just weeks after World War II broke out in Europe, for the MoMA exhibition Picasso: Forty Years of His Art.

The retrospective, including Guernica, traveled to Boston, Chicago, Cleveland, New Orleans, Pittsburgh, St. Louis, and San Francisco well into 1940. At the close of the exhibition, with war terrorizing Europe, Picasso asked that MoMA continue to safely house Guernica and about 95 other drawings and paintings he lent to the exhibition. These works remained at MoMA through the 1958 exhibition Picasso: 75th Anniversary, after which all but Guernica and its preparatory drawings were returned to the artist. These Picasso agreed to loan to the Museum indefinitely, stipulating that they be turned over to Spain only when Franco was no longer in power and democracy was restored.

The extensive traveling took a toll on the painting and its stretcher, however. Because of the painting’s size, each time it traveled the canvas had to be removed from the stretcher and rolled up, and the stretcher disassembled. MoMA’s founding director, Alfred H. Barr, Jr., described the process in 1969: “Picasso had too generously lent the Guernica about twenty times all over Europe and the U.S.A. The painting had been rolled, packed, shipped, unrolled, stretched, hung, and then unstretched and rolled, not counting the times when our Museum re-installed it after its return from elsewhere” (Dorothy C. Miller Papers, VI.B.I. MoMA Archives).

As early as 1957 MoMA’s painting conservator Jean Volkmer first wrote to Barr about the need for a new stretcher. The wood had deteriorated and become weak with the frequent disassembly, and Volkmer explained that the canvas was “drooping off an inadequate strainer” and that the size and weight of the canvas made it impossible to pull taut manually. The only solution was by “mechanical means”—a new, lighter stretcher with an expansion bolt design that, by using adjustable hardware in the joints, would provide strong, lasting support to the canvas. Though MoMA did not own Guernica, Barr, Volkmer, and the staff felt it was their responsibility as the painting’s caretakers to replace the original stretcher in order to preserve the work.

A new stretcher was indeed built by MoMA’s then-framer Andrew Olah, but it would be seven years before an opportunity to replace the original stretcher arose. On the occasion of MoMA’s 35th anniversary and the opening of the Museum’s new building in 1964, Guernica was reinstalled in a new location, providing an opportunity to restretch the canvas on the new stretcher. At that point, Guernica’s original stretcher must have been sent to storage for safekeeping.

In 1981 the Museum returned Guernica to Spain and the new stretcher went with it. The original had been forgotten, never recorded or cataloged, nestled among MoMA’s ever-growing collection. For the past 52 years this well-traveled, timeworn stretcher has inconspicuously remained in our carefully monitored storage, surviving two building expansions and a move to a new facility, where it has been cared for by our diligent staff. Now the stretcher, and its 80 years of history, will travel to its final home in Spain for the first time.

Rediscovering Guernica’s stretcher was a tremendous joy, reminding us of the work’s long history at the Museum and demonstrating how very much alive and filled with treasures our collection storage is. Thirty-five years after then-director Richard E. Oldenburg shared news of Guernica’s departure from MoMA with his staff, his words again resonate with us: “It has been a very great privilege and a tribute to this institution to have had this work entrusted to us for so many years […] we can take comfort and further pride in parting with it with good grace, with all possible concern for Picasso’s wishes and with due recognition of the special significance which Guernica has for the people of Spain” (Guernica records, correspondence 1960s, MoMA Archives). Today, we take similar pride in continuing MoMA’s commitment to the history of modern art, sending the original stretcher to the Reina Sofia for its Guernica archive so that the historic painting’s full story can be told.