Situated high on a bluff outside San Diego, a perfectly symmetrical canyon of raw concrete rises four stories from a travertine plaza. Down its center, a stream—known as the “channel of life”—traces a path that appears to vanish into the Pacific. This is the Salk Institute for Biological Studies, and it is widely considered to be the consummate work of celebrated midcentury architect Louis I. Kahn.

The dramatic setting and stylistic departure from its Southern California neighbors make the Salk Institute the quintessential architectural pilgrimage site. Thousands come every year for an experience that borders on spiritual. The building is evidence of the unique partnership Kahn formed with Dr. Jonas Salk, the developer of the first polio vaccine—their shared appreciation of nature and technology led them to collaborate on what is not only one of the great structures of the 20th century, but also one of the most important centers for biological research on the planet.

Salk Institute for Biological Studies, La Jolla

In many ways, the building has been easy to manage because it was so ahead of its time when it opened in 1963, says Tim Ball, senior facilities director at the Salk since 2008 and the building’s passionate steward. He points to Kahn’s prescient embrace of sustainable technologies: The offices are designed to siphon breezes from the ocean, green roofs stealthily stitch across the campus, and rainwater is collected and reused in an underground cistern.

“This was all design from 1958 to 1964 which we would call LEED Platinum rating today,” he says. “The groundwork that was there gave us the ability to take those technologies and put them into place today in a way that preserves the original design intent.”

The Salk has been responsible for major breakthroughs in neurobiology, genome mapping, and stem cell research. Elements of the design, such as the way natural light illuminates the underground labs through a series of courtyards and the open plan that requires members from different departments to circulate among study towers, have been cited by the Salk’s scientists as influential to their research.

But as the building neared the half-century mark, it was clear that certain aspects needed a more interventionist approach. “A lot of decisions weren’t made right away because Salk had run out of money to complete the project, so parts were unfinished for a long time,” says Ball. With scientists eager to move into their labs, some details of the design, like Kahn’s recommendation to add window flashings, were never implemented, leaving Ball’s team to contend with decades of leaks and water damage.

In his role, Ball sees an opportunity to not only fully realize Kahn’s vision, but to also potentially improve upon it—using a scientific approach, of course. “When we talk to our researchers here about the things that we’re doing to maintain, improve, and even expand the facilities, we liken it to the human body,” says Ball. “We have the nervous system, the lungs, the brains, the heart.”

After gutting the building’s mechanical processes over the last decade—replacing all the electrical systems, updating the data networks, and upgrading the plumbing—it was time to address the institute’s problematic exterior. To extrapolate Ball’s anatomical metaphor, the Salk suffered from a debilitating skin condition.

Once a neutral, uniform golden brown that provided a textural counterpoint to smooth expanses of concrete and travertine, the building’s 203 teak shutters had become stained and discolored. Depending on the location of the window—the oceanfront site creates what are essentially dozens of microclimates around the building—entire shutters had an almost tie-dyed appearance, with extreme variations in tone ranging from a bizarre reddish-orange to a dark gray.

In some places, the wood had turned completely black.

Getty Conservation Institute, Los Angeles

The problem at the Salk was first logged a few years after the building was completed, noted in maintenance records as a “five o’clock shadow” on the structure’s windows. Dr. Salk was so alarmed by the wood’s appearance that he summoned the project architect, Jack MacAllister, back to the site. MacAllister sent word of the problem to experts at the U.S. Forest Service, who prescribed regular cleanings using a bleach and water solution. Workers scrubbed. The shadow faded. But over time the shadow reappeared.

Fifty years later, it was clear that this strategy was not sustainable—and the problem was getting worse. The wood had been severely eroded from decades of scraping with stiff brushes. Termites had invaded the moist sections of the window frames, which had never been properly weatherproofed. The teak had deteriorated due to exposure, especially on the ocean-facing sides, leaving the surfaces even more vulnerable to whatever was slowly discoloring them. And although Kahn had left explicit instructions not to stain or paint the teak, it was clear that more than just bleach and water had been applied to some windows in attempts to arrest the creeping blackness.

“Because of all these varying conditions, they initially thought they might need to do a full replacement project,” says Sara Lardinois, a project specialist for the Getty Conservation Institute, which began working with the Salk in 2014. “But we were worried that could jeopardize the site’s cultural significance.” And since the wood was teak—specifically old-growth Burmese teak—there were new sustainability issues with its sourcing. “It’s a natural resource, and you have to think about being careful in its conservation as well.”

Through the Getty Conservation Institute, Lardinois’s work largely focuses on the protection of cultural antiquities, like conserving King Tut’s tomb while still allowing tourist access. But in recent years, the GCI, which was established in 1985 to help repair and restore art around the world, has expanded to encompass the conservation of modern architecture. Although the Salk is several millennia younger than some of the cases the GCI has taken on, the project was a unique opportunity to gather data on materials that hadn’t been addressed by the GCI’s research, while applying the same historical perspective the researchers bring to sensitive, centuries-old sites.

Lardinois proposed an investigative approach: They would determine Kahn’s original intent for the windows by examining historical archives and building records, conduct oral histories with people who had worked directly with Kahn or maintained one of his structures, and provide a forensic explanation for the shadowing—determining what was discoloring the teak and making recommendations for how to repair it. “Anything,” says Lardinois, “that could prevent these extreme variations in color.”

The Getty’s final report would also include a detailed conservation management plan for how to protect the building going forward. “It’s new to them, thinking about how to conserve a building rather than just maintain,” she says. “So it’s getting them, institutionally, to shift their thinking about their building.”

Just convincing the caretaker of a 50-year-old building that modern architecture needs to be conserved can be difficult, says Susan Macdonald, head of field projects for the CGI. But in her experience, a piece of modern architecture is often more vulnerable than a 100-year-old building of brick and stone.

“Modern architecture is more experimental than traditional architecture in that architects were using completely new materials or old materials in completely new ways,” she says. A long list of potentially problematic materials, from a conservation perspective, reads like a primer of modern design: plastics, plywood, fabrics, metals, concrete, laminates, flat roofs, thin metal-framed windows, sealants—some of which really only last a few dozen years in actual-use conditions.

As the Getty began to take on modern architecture conservation projects, it became apparent that these buildings needed to start cycles of repair much sooner than traditional buildings, says Macdonald. “So in a traditional building, you might say 60 years to its first good repair and 120 to its first really major repair. For modern buildings, we saw that 30 years is when you’ll need some repair, and at 60 years you’re getting to the first major repair. That’s half the time.”

With the Salk Institute, the Getty could help protect one of the country’s most important pieces of architecture, but also learn a great deal about a structure that has many commonalities with other modern icons. Sharing what they learned at Salk might help other owners of modern architecture to tackle their own conservation issues—before it was too late.

Margaret Esherick House, Philadelphia

In 1959, Kahn designed a boxy stucco and concrete residence for Margaret Esherick, a Philadelphia bookseller who wanted a quiet place to store and write books on a leafy cul-de-sac in the city’s Chestnut Hill neighborhood. With warm interior details crafted by Esherick’s uncle, a well-known woodworker, it has been celebrated as one of Kahn’s most handsome homes.

Esherick died just four months after moving into the home in 1961 and it had three owners over the next several decades. Despite its critical acclaim and auspicious location—it’s just down the street from the famous Vanna Venturi House, the postmodern landmark that Kahn’s friend, architect Robert Venturi, designed for his mother the same year—it failed to sell at auction in 2008, then languished on the market for several more years. Daniel Macey and Paul Savidge purchased the home in 2014 for just under $1 million and have so faithfully massaged it back into mint condition that the duo won a Docomomo award last year for its restoration.

Macey and Savidge were among dozens of Kahn homeowners and architecture experts tapped to participate in a workshop convened by the Getty to gather information for the teak window restoration. They sat in the University of Pennsylvania’s library with fellow Kahn stewards, poring over the original plans for their houses and listening to lectures from famous wood scientists. “It was an amazing experience,” says Macey. “By analyzing what he had done other places, they were able to use that information to help the Salk building.”

Kahn designed nine houses that use wood as a key material, but the Esherick House was of particular interest to the conservation team. Kahn was designing the house at the same time that he was designing the Salk, so he was making many of the same decisions and using many of the same materials, down to the hardware, like the system of hooks and pulls to open and close shutters. In fact, the Esherick House has the same style of wooden window walls as the Salk. And Macey and Savidge had faced many of the same challenges in figuring out how to protect them from water damage while preserving Kahn’s wishes.

“Apparently there was some quote that he had said, ‘Let the wood age naturally,’” says Macey. Even though that statement alone might dictate a completely hands-off approach, Macey and Savidge also believed Kahn embraced new technology and was accepting of changes that served future residents. He had even designed an addition to the house for a potential buyer after Esherick died (the addition remains unrealized). “He was very cognizant of the next generation,” says Macey. “He realized the same people wouldn’t live in that house forever.”

After much research, Macey and Savidge opted for a stain that acts as a moisture barrier, which protects the house well, but tints the wood reddish. Now, thanks to their connection to the growing network of fellow Kahn preservationists, they’re exposed to new “what would Kahn do” solutions. They’re keeping an eye on the exterior of the Korman House, for example, Kahn’s last residential commission, where the son of the original homeowners has started to reverse some of the interventions made since the home’s 1974 completion. The cypress exterior, once also reddish, is now turning gray—looking like a Cape Cod cottage in the woods of Pennsylvania.

That may have been Kahn’s original idea for their home, and for the Salk, says Macey. When Nathaniel Kahn, Louis Kahn’s son, who made the documentary My Architect about his father, came to visit Macey and Savidge, he was talking about his mother—legendary landscape architect Harriet Pattison—who had a home in Maine, where weatherbeaten wooden shingles dominated the built environment. “All of a sudden it dawned upon him that Kahn had been there,” says Macey. “Maybe the graying wood, aging naturally, was part of the plan.”

Getty Conservation Institute Science Department, Los Angeles

In 1967, a sample of Salk’s troublingly tinted wood was mailed to the Forest Products Laboratory, the Madison, Wisconsin, institution where the U.S. Department of Agriculture tests and analyzes wood products. Scientists there confirmed that the darkening effect could be attributed to the presence of microscopic black dots on the surface of the teak. The lab’s best guess was that, due to the coastal location, these were algae spores originating from offshore kelp beds.

But the scientists were limited to what they could observe using 1960s-era technology, says Joy Mazurek, a biologist for the Getty Conservation Institute. When she received samples of the Salk’s shadowed teak as part of the GCI’s investigation and placed it under one of the Getty’s powerful microscopes, she immediately realized that these were not algae spores.

“It had a cellular structure,” she says. So Mazurek put a few of the samples in water—and they started to grow. That’s when she realized she was dealing with a potentially destructive organism, she says. “It’s alive.”

Mazurek sent the samples off to a microbial lab for DNA analysis. The lab confirmed that it was a member of the order Capnodiales, meaning it was a type of black sooty fungus. This particular sooty fungus was the same kind that thrives on eucalyptus trees.

One of the most striking elements of the Salk Institute campus is its eucalyptus trees. The original 27-acre site was a pristine eucalyptus grove, with the building designed to sit among the stands of silvery leaves, which spin in the offshore breezes like a kinetic art installation. Even more eucalyptuses were planted after the construction of an annex in the late 1990s, which required some of the older trees to be removed.

To confirm her hypothesis that the eucalyptus was the source of the fungus, Mazurek analyzed samples from the trees on campus and from teak furniture in a plaza near the annex. Soon she started to notice the same fungus was present on other La Jolla buildings, she says. “My working theory is that it’s this ecosystem that feeds off of each other.”

The discovery of the fungus was both good news and bad news. The good news was that this type of fungus wasn’t eating the wood, says Mazurek. “It’s a biofilm—it doesn’t destroy the lignin, so it’s more of an aesthetic problem.” The bad news was that, short of chopping down all the eucalyptus trees in La Jolla, the fungus wasn’t going away, she says. “It’s in the environment—you can’t get rid of it.”

Since the fungus was known to thrive in the presence of moisture, it was clear that waterproofing the windows needed to be a priority to prevent the accelerated growth that was threatening the integrity of the north-facing shutters. But the GCI’s scientists also had to figure out what previous maintenance teams had used to treat the wood—and if those treatments had caused any additional discoloration or damage.

To look at the history of surface coatings, Mazurek and her colleague Herant Khanjian used infrared spectroscopy and gas chromatography–mass spectrometry, two processes that are often used in conservation analysis to examine the chemical makeup of paint and other materials. By analyzing cylindrical holes drilled into the deteriorating shutters, they could chemically map the teak to trace the history of past interventions and how they affected the wood.

The scientists were able to isolate at least five or six different coatings that had been applied to the teak over the years, from acrylic lacquers to formaldehyde polymers to biocides to wood oils. After correlating their findings with maintenance logs, the scientists even confirmed the presence of a specific oil sealant used on boats, named Tip Top Teak. By artificially aging pieces of new teak treated with Tip Top Teak, they determined that this was almost certainly the product that had turned the wood reddish in the 1970s.

Wiss, Janney, Elstner Associates, Pasadena

After the Getty’s fungal findings helped determine a new maintenance strategy, the larger challenge emerged—how to address the existing discoloration of the windows. This job fell to Kyle Normandin, associate principal at Wiss, Janney, Elstner Associates, Inc., the firm that served as architect of record for the restoration process.

The original windows had been prefabricated off-site by a local cabinetmaker, shipped to the site on a flatbed truck, and hoisted into place. Wiss, Janney, Elstner built 16 different mockups of the windows, experimenting with various repair methods that could preserve the original wood. In the end, about two-thirds of the window elements were retained, including all the frames. Most of the wood that had to be replaced was in the tongue-and-groove assembly of the shutters, says Normandin, where deterioration could be attributed more to direct sunlight than water damage.

Miraculously, the team was able to locate old-growth teak from Burma (now Myanmar), which they analyzed with wood scientists at the holding yard in Maryland to ensure the cuts they chose would match the grain of the existing pieces. As Lardinois predicted, the procurement of similar teak will become even more difficult in the future due to the country’s efforts to stop deforestation. “Two months after we placed the order there was a moratorium from the State Department,” says Normandin. “You can no longer get old-growth teak from Myanmar.”

Meanwhile, teams were busy applying a variety of treatments to dozens of wood panels that sat on the roof of the Salk for months, where the team could watch for discoloration or deterioration. Separate trials were taking place in Wiss, Janney, Elstner’s lab to determine how to treat the new wood to match the old wood.

After surveying the wide range of options, the Salk’s management selected a very thin coating that added minimal color, tinting the wood a shade that was closest to freshly milled teak. In addition to an anti-fungal cleaner to prep the wood, fungicide was added to the treatment, along with an ultraviolet light inhibitor. “We know we’re not going to be able to stop the degradation,” says Normandin. “The best we can do is slow it down.”

As part of the window installation, the team also added new detailing and sealants around the glazing to finally provide adequate weatherproofing. Just after the installation last winter, Southern California was treated to a series of particularly intense storms. For the first time, these windows did not leak.

The Salk has now established an architecture endowment to help fund preservation work. Wiss, Janney, Elstner is drawing up a long-term conservation schedule and will remain onboard as the consultant to any future interventions. The exterior walls are probably next: While the scaffolding was up, Normandin’s team was able to analyze damage to the concrete and begin to make recommendations for its repair.

As a new chapter for the Salk begins, even the most astute architectural observer might have trouble placing a finger on exactly what has changed. “Some people just say, ‘Wow, you cleaned the windows,’” Normandin laughs. “But that’s actually a really good compliment. We’ve done it in a way that’s non-intrusive.”

What the conservationists may have also done is reset the Salk, allowing Kahn’s original design intentions to finally emerge.

Louis I. Kahn Collection, University of Pennsylvania School of Design, Philadelphia

Sooner or later, all questions about Kahn make their way to William Whitaker, the curator and collections manager for the University of Pennsylvania’s architectural archives. The entire contents of Kahn’s office when he died in 1974, including thousands of drawings, models, and pieces of correspondence, are on permanent loan here from the Pennsylvania Historical and Museum Commission.

In recent years, Whitaker has taken on another role as the connector between homeowners, conservationists, architects, and scientists who are looking for answers about their Kahn projects, often about wood. And Whitaker believes that Kahn meant for the Salk’s teak to turn gray—“silvering,” he calls it.

“Kahn was very consistent about it,” says Whitaker. The architect often referenced old barns in pastoral settings or a fisherman’s house on the ocean as inspiration in his lectures and his writing. “He always sought out a silvery quality—the sense of wood as it ages naturally on the landscape.”

It’s difficult to know exactly what shade he meant to achieve using teak. Kahn only used exterior teak in one other location, the Phillips Exeter Library in New Hampshire, where it was subjected to frost and freeze—and no eucalyptus trees—which have aged the wood in a radically different way. Now that institution is about to begin its own conservation process, says Whitaker, and will rely heavily on what was learned at the Salk and as well as help inform the Salk’s maintenance going forward.

Whitaker commends the Salk team for not staining the wood gray outright. “With a Kahn building you can never make it perfect,” he says. “There are always these subtle imperfections on the surfaces. The team that has done this work understands this profoundly. The aging process is as critical as the architecture.”

It’s perhaps the most poetically appropriate resolution for a site known for its world-changing science: The 50-year mystery that may have revealed the true intentions for the Salk could only be solved by a biologist. With a little help from technology, now the Salk can let nature take it from here.

But the story is in no way over, says Whitaker. “With that aging silver wood in the years to come, what will emerge is this little bit of extra character that Kahn had in mind,” he says. “In some ways, we’ve never really seen the Salk.”