WASHINGTON, D.C. — Under a bright, azure sky that stretched past the Washington Monument and the National Cathedral one morning in late March, George S. Sexton III climbed onto the roof of a four-story office building in Georgetown and ducked into a small gray structure that looked as if it might have been left there by a tornado, like Dorothy’s farmhouse in “The Wizard of Oz.”

The inside of the plywood box had a “you’re not in Kansas anymore” quality, too. Sexton sat down in a swivel chair at its center to be eye-level with the “floor” of his firm’s scale model for one of the 20th century’s most important art sanctuaries, Houston’s Rothko Chapel.

Ignoring prints of Mark Rothko’s paintings glued to the model’s walls, Sexton examined the ambient glow cast by an octagonal piece above his head, a laser-printed plastic skylight with panels made of tiny, fixed Venetian blinds. The daylight fell slightly brighter on one wall, indicating “the subtle directionality” of the sun through the louvers. Exactly as he wanted.

With this model, the renowned lighting designer may finally resolve a conundrum that has dogged others for 48 years: How to create the sublime experience Rothko envisioned for his light-absorbing paintings and the skylit interior created around them.

“There’s going to be more light on the wall, and it will be more even, with less light on the floor,” Sexton said. “I think you’re going to see more things happening in the art. That may be a shock.”

Commissioned by John and Dominique de Menil in 1964 and completed in 1971, the chapel was supposed to be a profoundly moving marriage of art and architecture. For years, though, many visitors have found it dark and depressing. Chapel regulars tell a story about one person so mystified she asked, “Where are the paintings?”

Even the artist’s son, Christopher Rothko, admits there are days when the space doesn’t speak to him.

“The chapel has a certain serenity to it because of the paintings’ size and the acoustical properties of the space,” Sexton said. “Sometimes serenity can be confused with depressing because it’s quiet and calm.”

A baffle that’s hung below the chapel’s skylight for about 20 years also made the paintings seem blacker than Rothko probably intended, compressing the room’s proportions. Without it, though, the chapel’s light is so bright it damages the paintings.

The big baffle was “quite powerful, in a negative way,” said Stephen Cassell of Architecture Research Office. “It felt like a void that competed with the paintings. Technically it made a lot of sense, but it undermined the goal.”

Cassell is the lead architect of a $30 million project that includes other chapel improvements, several new buildings and a meditation garden on two acres between the Menil Collection and the University of St. Thomas. The chapel closed in March and is shuttered the rest of this year for Phase I, as fundraising continues. (To date, the capital campaign has raised $10 million.)

Even before visitors encounter Sexton’s skylight, a new grove of trees will help their eyes adjust as they enter the building, part of the landscaping plan by Nelson Byrd Woltz.

“There are going to be a lot more trees, and they’re making the plaza a slightly darker value, so your eye will begin to transition,” Sexton said. “Depending on your age, it can take 30 minutes for the eyes to fully adapt. I’m trying to reduce that. The longer someone spends, the more they’re going to see.”

As part of this “procession,” Cassell is removing the chapel’s front desk and other impediments such as the constant hum of air conditioners. “Every small detail can take away from your experience,” he said. “It’s about your eyes but also about mentally leaving the world. And when you come out, we’re giving you space to decompress and think about what you’ve experienced.”

Carol Mancusi-Ungaro, who probably knows the canvases better than anyone, thinks some first-time visitors may always be disappointed because they expect to see a traditional chapel with an altar, nave and some decorative paintings. Rothko’s 14 monumental canvases and the space that surrounds them comprise a single, total work of art — a concept that’s not easy to grasp.

That’s one of the wonders of the place, and why some people can barely stand still in it. Their eyes want to spin around the room. “Rothko was challenging you to look into yourself,” said Mancusi-Ungaro, who led the Menil Collection’s conservation department 20 years before joining the Whitney Museum of American Art.

That won’t change, nor will the challenging darkness of the paintings. But they are neither solid black nor minimal, as many people think, Mancusi-Ungaro said. “They are very much about proportion and scale (in relation to each other) ... They’re about light — the way light falls on them and the feeling it evokes in the viewer, which can be spiritual.”

Johnson vs. Rothko

If architect Philip Johnson had had his way, the Rothko Chapel would be a white plastered building topped with a towering spire and a small oculus at its peak; not a quiet, earthbound and wound-into-itself brick building.

One has to wonder why the de Menils paired Rothko with Johnson when the artist and the architect were still fuming over a previous commission. Johnson hired Rothko to create murals for the Four Seasons Restaurant in New York’s Seagram Building in 1958. Rothko responded with masterpieces but returned the money and refused to deliver his paintings to a setting he considered pretentious.

The de Menils owned several of Rothko’s earlier, brighter paintings; and they had hired Johnson to design their Houston home and the campus they built for the University of St. Thomas. The chapel project gave both men a dream job, but once again, their agendas clashed.

Johnson wanted to create an attention-getting focal point of his mall at the Catholic university. Rothko did not want architecture to overpower his art. He wanted an unadorned, democratic space, and none of Johnson’s revisions satisfied him.

Johnson quit after the de Menils sided with Rothko. Meanwhile, the couple had a falling-out of their own with the university and moved the chapel site to their own property across Yupon Street.

“It was a crazy time,” said architect Gene Aubry, who ended up shepherding the job after his partner, Howard Barnstone, fell ill. “Johnson and Rothko just could not deal with each other, which is kind of sad because they were the same kind of people.” On the sly, Aubry reenlisted Johnson to help with some of the chapel details.

Rothko’s contract stipulated that he would oversee the paintings’ final placement and lighting, and the artist seemed enthused about coming to Houston for the first time when Aubry visited his New York studio early February 1970. He had recovered from a heart attack, and the paintings were finished. Then, a few weeks later, Rothko killed himself in the studio, a 69th Street carriage house he had rented to make the chapel paintings.

He had built temporary walls there, the same dimensions as the planned chapel walls, so he could perfect the works’ scale, color and shape. He settled on three triptychs and five single panels. Seven are called the plum monochromes, and seven contain rectangular black forms within plum grounds. All involve layers of brick reds, deep reds and black mauves mixed with watery substances. Rothko was secretive about his medium; and only after intense research did Mancusi-Ungaro later discover the egg-oil emulsion component that reacted to the chapel’s humidity and bright light.

The chapel was designed with a skylight because Rothko’s studio had one. Likely grimy with age and shaded by surrounding buildings, it nevertheless attuned him to relationships between evolving daylight and the experience of viewing art. Rothko hung a parachute to create a diffused effect; that drove the whole concept of his late works.

That is another aspect of the legend: While Rothko had carefully planned the chapel space, he did not understand the intensity of the Texas sun. Christopher Rothko doubts that his father could have fixed the skylight issues if he had witnessed them, “but it would have been different,” he said.

In Houston, Aubry sketched a parachute-like scrim to cover the chapel’s first skylight, but it was never installed. He gets irritated remembering the black baffles that followed.

“People don’t understand how simple it needs to be,” he said. “Every time someone gets their fingers on it, they make it more complicated.”

Sexton’s solution

The goal now is not to replicate Rothko’s studio but to create an emotional experience that’s as close as possible to the artist’s intent.

Sexton said it’s all about subtleties. His basic techniques were developed at about the same time as the chapel, by mentors who knew Johnson and Aubry, so he feels his work has the zeitgeist of the original design.

“I think Rothko really had a concept. I don’t think the architects really studied what he had in his studio. I don’t think Rothko had any idea what Texas sky was like. The dots weren’t connected,” Sexton said. “We’re trying to connect the dots.”

Trained as an architect, Sexton got his first job in the early 1970s with Claude Engle, a pioneering lighting consultant and electrical engineer. Then he worked at several museums, including a stint as chief exhibitions designer at the Fine Arts Museums of San Francisco. Along the way he also learned from industry legends Edison Price and scientist Isaac Goodbar, who patented track lighting and “wallwasher” fixtures for museums and skyscrapers by leading architects.

The louvers for the new chapel skylight are very much Edison Price-Isaac Goodbar inspired, Sexton said.

Other louver systems Sexton has designed during the past 20 years softly illuminate Andrew Wyeth watercolors at Pennsylvania’s Brandywine River Museum, centuries-old tapestries in a vaulted gallery at Connecticut’s Wadsworth Athenaeum, and oil paintings at Florida’s Ringling Museum of Art. “So I know they work,” he said.

But scale models such as the one above his office is very much a Sexton innovation, and critical to predicting how daylight will perform in a building.

“You can run numbers and computer models to understand some qualities, but you also have to actually put your head in and be there,” said Owen Brady, the George Sexton Associates partner behind the new skylight’s geometry, angle studies, computer models and the 3D laser-printing of the mini-skylight. “A large-scale model is really the only way to experience daylight, and to get a feel for what it’s like to be in the space.”

The louvers will direct daylight onto the chapel’s perimeter walls. Brady has measured light inside the model during different seasons, sometimes hourly, for almost a year, to select just the right gray paint finish for the skylight’s metal frame and the louvers —aiming to “calm” the chapel’s new, flat-textured ceiling by eliminating severe, raking light.

Night lighting

The chapel’s night light has been been as troubled as daylight, added for seminars and performances Rothko probably did not envision. Sexton has designed a system of concealed video projectors and mirrors that will accommodate events but cast low, even light onto the paintings. He knows that technology works, too; he used it to illuminate the super-fragile remains of the Star Spangled Banner (the flag that inspired the national anthem in 1812) at the Smithsonian National Museum of American History.

Crowds access the Star Spangled Banner through a tunnel-like hall where the energetic din of a bright lobby quickly recedes. On a recent day, visitors were hushed and reverent in that space, which is many times darker than the chapel’s night lighting will be.

“You’ll be moving from a dynamic experience during the day to a static experience at night,” Sexton said. “But we think it will be a very beautiful, controlled experience. Into dusk and the evening, before the artificial lighting is turned on, the paintings will be dark and may still seem depressing,” he added. “The whole point is, it’s an organic experience.”

After he emerged from the model recently, Sexton popped off a triangular section of plastic skylight about the size of a huge slice of deep-dish pizza. A screen of translucent fabric on the bottom softened the industrial look. Diffused glass will top the actual skylight, to be built soon in the Midwest. Will it matter that the model was tested under D.C. skies, 1,400 miles northeast of Houston?

“Every location has its own quality of light,” Sexton said. “But at any one point, the light is always the same.”

Christopher Rothko, knowing chapel regulars are sensitive to change, expects the renovated space to feel “quietly revolutionary…like a veil has been lifted and you have more air to breathe.”

Mancusi-Ungaro admires Sexton’s understanding of light and his respect for Rothko’s paintings. “For the first time since the opening, people will get a sense of the space as Rothko intended,” she said.

“The Rothko Chapel is an extremely important work of art. If viewers can drop everything, including their cell phones, and just be there, it’s an extraordinary spiritual and art experience.”

molly.glentzer@chron.com