Ludwig Mies van der Rohe’s goal as an architect was to use emerging technology to build something besides fortresslike rock piles, to create buildings that were “almost nothing.” In 1921 he proposed a skyscraper whose walls were made entirely of glass. It would be over a quarter century before he could achieve this vision, and it would happen not in his native city of Berlin but in his adopted home of Chicago.

Mies emigrated here in 1938 to be the architect for the new Illinois Institute of Technology campus, on State Street between 31st and 35th streets. But administrators and finances forced him to keep his early buildings simple, with lots of brick. He came closer to achieving his heroic ideal after World War II, with glass-walled structures such as the high-rises at 860-880 N. Lake Shore Dr. and the Farnsworth House in Plano. Finally IIT let him design a building for his own department of architecture.

That building, the 1956 Crown Hall, would be the purest working out of Mies’s dual obsessions: achieving maximum transparency and creating the largest possible building with the least possible structure. He created a single open room–120 feet wide by 220 feet long by 18 feet high–whose roof is suspended from just four enormous girders, leaving the interior completely free of columns. The floor is gray terrazzo, the ceiling a continuous sweep of white acoustic tile. Along the building’s perimeter the structure was pared down to an ultralight steel frame surrounding huge glass windows. Each of the clear upper panes is a spectacular 11 and a half by 9 and a half feet. The window frames, the blinds, even the tables for the architecture students who worked there were designed by Mies, and everything fit together perfectly with simplicity and grace. The result was a communal space that eloquently expressed the idea of freedom within order.

The intervening years have not been kind to Crown Hall. Moisture that got into the highly porous travertine marble used for the south porch froze and expanded over many harsh winters, cracking and crumbling the stone. Rust attacked the often poorly maintained steel frame and made the air vents inoperable. Peter Beltemacchi, associate dean at IIT, says the white blinds over the windows turned yellow from “tar and nicotine and haze and age.”

In 2003 Helmut Jahn’s State Street Village, the first new building on the campus in decades, opened up across the street from Crown Hall, faced in shiny corrugated stainless steel. It was soon followed by Rem Koolhaas’s riotous McCormick Tribune Campus Center to the north. Koolhaas claimed that the blazing orange glass in his building helped set off the color of the older buildings on campus, but Crown Hall’s black paint had faded to a smudgy gray. It remained a shrine to Mies and modernism, but it had become like a beloved old aunt. You might bring her flowers, but if you were looking for a good time you’d call Jahn or Koolhaas.

Crown Hall just reopened, after the $3.6 million second phase of its restoration, and it’s never looked better. The sleek, shiny black of the new paint job is as vivid as Koolhaas’s orange–and a lot more elegant. Beltemacchi remembers that the original paint was the same black. “Mies was very proud of it,” he says. “It didn’t turn gray for a year and a half.” The restoration project’s architect of record, Mark Sexton, says it wasn’t easy for the contractors to get the new paint exactly right. “They would spray an entire elevation, and we would reject the entire elevation,” he says. “They would say OK. And they sprayed the entire east and south elevation, and we said, ‘Rejected.’ The amazing thing is that there was very little whining. They were actually very conscientious.”

Replacing the building’s 340 windows wasn’t easy either. The original glass of the upper windows was a quarter-inch thick, and it moved and sometimes broke in the wind. City code now requires glass to be a half-inch thick. “As glass gets thicker it gets greener,” says architecture dean Donna Robertson. “We switched to what is a low-iron glass–some people call it the superwhite glass. There are only two manufacturers from whom we could buy a piece of glass of that type in this size. It took ten men and a crane to hoist the glass in the air and then slide it into the steel frame of the building.”

Each of the massive new panes weighed 700 pounds, more than the original Mies-designed “stop,” the piece of metal that holds the glass in place, could support. Arguments raged over “what would Mies do,” and the decision to go with a slightly heavier, trapezoidal stop was opposed by the purists as a betrayal of his commitment to right angles. Unlike the originals, the new stops had to be custom-made. “There’s a lot of scrap metal out there, because huge amounts were rejected,” says Sexton.

The smaller, lower panes of glass presented another problem. Mies’s originals had been sandblasted to create a translucent white finish. They were replaced in 1975 with two eighth-inch panes of glass and a plastic film sandwiched in between, but these laminates were less translucent than opaque, casting reflections back into the building. Sexton and his colleagues compared more than 100 types of glass, then mounted the five full-size finalists in the hall’s north facade next to glass that matched Mies’s originals. The final choice was a sandblasted glass that achieves the translucency of the original.

Free of controversy was the restoration of the vents along the bottom of the windows. Mies’s later glass boxes would become sealed environments dependent on mechanical air-conditioning, but Robertson says he was a “protogreen” architect who “understood natural air.” Fresh, cool air flowed through the vents at floor level, and hot air flowed out through vents in the ceiling–a simple convection effect that’s been rediscovered by contemporary green architects.

Building managers tend to love sealed boxes because everything’s automated, but when Crown Hall opened, the lighting and ventilation system consisted of venetian blinds and a man named Ludwig Hilberseimer, who came with Mies from Germany and taught planning at IIT. “Hilberseimer used to walk around and adjust them all day long,” says Beltemacchi. “A lot of it was to get some light up onto the ceiling to get it out onto the tables. When he died in 1967, that’s when the venetian blind business went to hell. We don’t have anyone who does that anymore.”

Robertson and Sexton hope to get a surrogate during the third phase of the restoration, estimated to require another $5 million. “We’re going to cut down on the energy consumption of this building, which we can do very dramatically in terms of electricity,” says Robertson. “We’re going to build a building brain that will automate the blinds. Right now the concavity of the [blind] blade goes down. We’re going to flip that, so it goes up. That way sunlight is going to bounce further into the interior, rather than relying so much on the electrical lights. And the lights will be controlled by the building brain as well, because it will read what the foot candles are at any point in time.” Robertson also hopes to use the original radiant heating tubes in the floor to cool the building during warmer weather.

Mies once said that “God is in the details” but some architects think his attention to detail was much too anal–even the hall’s worktables were designed to fit the grid of the terrazzo flooring. Perhaps they see his controlled, linear, simple architecture as a relic of a despotic age. Yet the simplicity of Mies’s masterpiece, with its spare, paradoxically open enclosure, can be extraordinarily freeing. A story told by Peter Roesch, now a professor at IIT, about a day when Mies stopped to look at his work suggests a parallel between the way Mies taught and the effect his buildings can have on people. “The good news was that he didn’t walk away,” Roesch says. “The bad news was that I didn’t know what he didn’t like. He did not say one word for 20 minutes. It forced me to look at my own work, and I found all the mistakes–everything. After 20 minutes of silence, I said, ‘Mies, could you come back tomorrow? I’ll fix it all up.’ And he laughed, and he puffed his cigar, and he left.”

Art accompanying story in printed newspaper (not available in this archive): photo/Dan Kuruna, courtesy of Kreuck & Sexton.