Glass Breaks Barriers,
Becomes Design Staple

When Apple Computer Inc. converted an old post office in New York City's SoHo district into a retail store last summer, Chief Executive Steve Jobs wanted a look as distinctive as the company's own desktops.

The material of choice: glass. But not the fragile sort. The Apple store boasts a staircase with 8-foot-wide glass treads. At the top of the stairs is a glass landing and glass bridge. "People are fascinated," says Jaime Rojas, the store manager. "They touch it, they feel it."

And they can walk on it. Glass increasingly is being made with a transparent inner layer, which the industry prefers to call "inter layer," that can make it strong enough to withstand hurricane-force winds, bomb blasts and projectiles hurtling more than 30 miles per hour. Used in construction, this form of glass is comparable to concrete in strength.

Laminated safety glass, made with Polyvinyl butryl, or PVB, has been used in automobile windshields since 1938 and the industry spent few resources on innovating the product until the 1990s, when in Hurricane Andrew in South Florida and a series of terrorist bombings, including Oklahoma City, spurred government and industry researchers to develop a stronger glass with better insulating properties.

Chemical makers DuPont Co., Wilmington, Del., and Solutia Inc., of St. Louis, have been in the lead in developing a stronger kind of inter layer using PVB. The basic science hasn't changed much, but the lamination process has been refined so the PVB layer is thicker and stronger, and it is better sandwiched between glass to reduce the incidence of bubbling or water seepage between the layers.

Laminated glass doesn't break into shards like regular glass, nor does it break into pieces like tempered glass. Under extreme stress, it can crack like a windshield, but it still holds together. In lab tests the glass has withstood a nine pound two-by-four traveling at 34 mph. That's a particularly advantageous feature in hurricane areas: If a building's windows crack but hold firm in a storm, high winds won't blow through the structure and rip it apart. Consequently, laminated glass is being used for windows in coastal areas where winds can top 110 mph -- from New York's Long Island to Brownsville, Texas. The U.S. State Department is installing it in its buildings around the world to reduce the impact of bomb blasts. The glass was used in the reconstruction of the Pentagon, which actually had some of the super-strong panes installed just weeks before the Sept. 11 attacks. They were among the few that didn't shatter from the impact of the hijacked plane.

And the glass is used in as many as 25 vehicle models, including the Lincoln Navigator, the BMW 7 series and the Volvo Cross Country, not only to reduce so-called smash-and-grab crimes and car theft but also to reduce noise and block dangerous ultraviolet light.

But laminated glass may make its biggest impact in construction: It allows more natural light, minus the UV rays, into buildings while buffering against outside temperature extremes. For example, a Prague retail and office project known as River City includes a building with a glass wall six stories high. Gannett Co.'s headquarters outside of Washington also uses a clear glass exterior.

Architects say the strength, acoustics and insulation of such glass, as well as the ability to add colors or designs to its inter layer, eventually will make laminated glass the material of choice in U.S. buildings.

"It's about to break out," says John Durbrow, a professor at the Illinois Institute of Technology and former senior vice president at Chicago-based Murphy/Jahn architects. "The technology has been around for a long time, but of late laminated glass has become a more complex, more high-performance sandwich."

In addition to PVB-based laminate layers, DuPont also developed another type of product it calls ionoplast. It's an offshoot of the strong, rigid, high-performance plastics used in bowling pins. DuPont says the new product, used in Apple's SoHo store among other places, is 100 times stiffer and five times more tear resistant than glass made with PVB. Solutia says it is pursuing a similar product, but that the flexibility of PVB, especially in high winds, still makes the resin a desirable choice for lamination.

Laminated glass is about twice as expensive as regular glass, with more than half of it sold for use in making cars. In other North American hurricane markets sales grew 20% last year to roughly $500 million, says Nick Limb of Ducker Research Inc. in Bloomfield Hills, Mich. Overall, industry experts say the world-wide laminated glass market is about $3.5 billion.

In the past decade, Dewhurst Macfarlane, a structural engineering firm with offices in New York and London, has achieved several projects with laminated glass, among them the Broadfield House Glass Museum in Winsford, England, believed to be the first building to use glass beams and glass columns.

Besides, Apple's SoHo store, the company's first foray into Manhattan, stores in Chicago and Los Angeles also use laminated glass. Ron Johnson, senior vice president for retail, says the company first wondered whether people might hesitate to walk on glass for fear it might break. But he says the transparency of the material and the open feel of the store actually invites shoppers upstairs. "This makes you want to go up," he says.

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