Nestled in the Berkshires sits an understated jewel—the Stone Hill Center at the Sterling and Francine Clark Art Institute, a public art museum and research center established in 1955 by Singer sewing machine heir Robert Sterling Clark and his wife Francine. The Stone Hill Center “speaks” softly but leaves a lasting impression. So it is no surprise that the project, which opened in June 2008, did so without great fanfare in the design press.

Stone Hill is the first phase of a master plan for the Clark, meant to enhance visitor experience of its collection of 17th–19th century American and European art. The 32,000-square-foot center incorporates a meeting space and two small galleries that supplement the Clark's main exhibition spaces in the original museum. But the center's principal purpose is to house the Williamstown Art Conservation Center (WACC). Founded in 1977, the WACC is the largest regional conservation facility in the United States and serves more than 55 New England art institutions and private clients. Over the years, its reputation has spread widely.

In many ways, the Stone Hill Center can be considered the second phase of the Clark's master plan. The initial project was to be an exhibition, conference, and visitor center located across a parking lot from the two buildings that house the existing Clark galleries. A nondescript two-story building currently occupies that site, which was the WACC's home before it moved to Stone Hill. The WACC had to relocate to make way for the planned conference center, and it became clear to the museum administration that they needed to reorder their expansion plans. Plus, the WACC had outgrown its facility, so the new arrangement suited them just fine.

The design of Stone Hill is rooted in a long tradition of art and nature convening as one. Awareness of the natural landscape and a masterful use of natural light are hallmarks of the work of its designer, 1995 Pritzker Prize–winning architect Tadao Ando. The architect opened his practice, Tadao Ando Architects & Associates, in 1969, and has built mostly inside his native Japan. When the Clark selected him for the Stone Hill project in 2001, he recently had completed his first major works in the United States—the Modern Art Museum of Fort Worth in Texas and the Pulitzer Foundation for the Arts in St. Louis.

There are parallels between the three projects, including Ando's characteristically deft crafting of space and the use of concrete—his signature material, which he elevates to the stature of refined stonework. But Stone Hill utilizes the architect's design vocabulary to the greatest degree. Here, he takes advantage of the rural setting and celebrates it, creating a powerful yet sensitive architectural response to the site. The two-story Stone Hill Center is formed around a single design gesture, with the rectangular building's principal glazed façade oriented directly north. This one move allows the building to define itself and its connection to its surroundings and to light.

It is this connection to light that has earned the building's conservation labs recognition as one of the premier facilities worldwide, alongside the Getty Center in Los Angeles. No longer relegated to windowless, electrically lit subterranean rooms, the WACC celebrates the conservator and the conservation process, revealing it in spectacle-like fashion to the public.

Upon first consideration, natural light might seem like the wrong way to approach a lighting solution for an art conservation facility. Light levels in galleries are generally low, especially if delicate artwork is on display, to prevent exposure to damaging UV rays. But the issue of lighting for a conservation lab is about creating a series of short exposure times that allow conservators to operate in light conditions comparable to those of the original artists; with galleries, the issue is to minimize an artwork's cumulative long-term exposure to light.

The WACC operates four principal labs: one for painting, one for paper, one for objects, and one for furniture. With the exception of the photo lab, an X-ray room, and storage, there isn't a single space in the WACC that does not somehow come into contact with natural light. In fact, this was the conservators' main request—that they have a light-filled space, particularly in the painting lab, which occupies the north side of the building. Here, New York–based Fisher Marantz Stone (FMS), the lighting design firm responsible for the project, was tasked with providing two kinds of light: the natural light through the north façade, by which art is created, and a supplemental electric lighting system outfitted with halogen sources to mimic gallery conditions.

FMS also participated in the specifying of the window-wall glazing, a non-tinted low-E glass. Floor-to-ceiling windows deliver a cool ambient light into the space, creating a comfortable and pleasant working environment. The windows also are equipped with two sets of blinds—a diffusing shade and a blackout shade—that can modulate the amount of light in the labs depending on conservators' needs. But as WACC director Thomas Branchick notes, the blinds are used only on rare occasions—as are the linear halogen ceiling luminaries outfitted with elliptical reflectors. When extremely detailed work has to be performed, the conservators rely on patient exam lights that can be positioned near the artwork.

Even the paper lab, where one might expect natural light to interfere with conservation processes, benefits from its eastern-facing exposure. As Branchick explains, the new lab allows conservators to perform year-round sun bleaching, a less invasive process for removing discoloration on certain paper artworks than chemical bleaching. Sunlight, coupled with white diffusing shades if needed, allows for greater control and a more gradual manipulation of the bleaching process.