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Could They or Couldn’t They?
Why the Glass on the 1 WTC Podium Won't Create Rainbows

by Tara Taffera

One World Trade Center (WTC). It was supposed to be a jewel rising from the dust of the former WTC towers. The architect envisioned cladding the base of the building in light itself. Light refracted and sent dancing by millions of prisms cut into the glass. Light that would belie the dark history of what was once referred to as The Freedom Tower. The world, and most especially the glass industry, watched eagerly as the plans for this unique building unfolded.

And then suddenly, after years of preparation, it was announced in May 2011 that prismatic glass would not clad 1 WTC after all. The rainbows could not be made. Or could they?

The decision has industry experts questioning whether those in charge—the Port Authority of New York and New Jersey (PANYNJ), along with SOM architects and Tishman Construction—made a wise decision when they collectively abandoned the concept of prismatic glass (see June 2011 USGlass, page 12). Perhaps the PANYNJ should have ceased its contract with the fabricator that reportedly had problems creating the complex prismatic glass panels. The parties involved may have had other options available to them that, until now, have gone unreported. Is prismatic glass a viable solution for buildings such as the WTC? Experts have differing opinions.

First, a definition of prismatic glass from a few who have worked with the product. “Prismatic glass has been cut and highly polished to the degree that it breaks white light into a full spectrum of colors,” says Kenneth von Roenn Jr., president/director of design for Architectural Glass Art Inc. in Louisville, Ky.

Nathan Munz, managing director of Glassform, an Australia-based fabricator, believes there are various levels of definition for this term, depending on the specifier’s design and performance requirements.

“The most basic [definition] would only require that the glass has facets, which give it a number of surfaces at an angle to the plane of the glass (as a prism has),” he explains.

The Vision Unveiled, Before It Failed Having a hard time visualizing the original design for the WTC podium wall? Architect David Childs envisioned making the prismatic glass come to life. In presenting his final design for the tower base in June 2007, he described how the outside face would be made up of prisms. “Some panels would have very big prisms and some would have small prisms to give a fluctuation and a character to it. When sunlight hits that prism it splays into color,” he said. This is a very new idea about the base—one that we feel strongly about,” said Childs, who added that the glass would be made of a laminated safety glass—“so if it breaks for any reason it doesn’t fall in shards.” Visit http://www.wtc.com/media/videos/David%20Childs,%20SOM to view the video.

A Quick Refresher
The original design for the podium wall of 1 WTC was to cover the concrete base with prismatic glass (for the original investigative article detailing the WTC construction, see April 2009 USGlass, page 30). According to the SOM website, “The podium wall base is 186 feet tall and its cladding is being designed to create a dynamic, shimmering surface that animates the experience of the building at ground level” (for more on the original design see the website in the box above).

The contract for the installation of the podium wall was awarded to Solera/DCM Erectors, based in New York. DCM hired a subcontractor, Zetian Systems Inc., based in Las Vegas, to perform design assist services, fabrication and delivery. Zetian awarded PPG Industries, based in Pittsburgh, the glass contract. PPG was to supply its Starphire ultra-clear, low-iron glass to Zetian. Zetian, in turn, had contracted Sanxin Glass in Shenzhen, China, to fabricate the Starphire glass into the prismatic panels. (For more on Zetian and its role in the project, see May 2011 USGlass, page 35.)

But in May it seemed the plan fell apart. “As design moved to the testing phase, it became clear that the prismatic glass simply had too many technical problems to overcome and at a budget that was not cost-effective. We have been finalizing a design that will be far more practical while being both distinctive and magnificent,” John Kelly, a spokesman for the PANYNJ, told The New York Times in May (The Port Authority would not return calls from USGlass).

The article also stated that the new façade is likely to be made of more traditional clear glass panels, possibly with granite elements to tie it into the surrounding plazas.

So it seems all of those parties above are out—unless they choose to bid on the new design—and SOM is starting over. Elizabeth Kubany, public relations representative for SOM, told USGlass in late August, “The client is reviewing our designs and we expect them to select one for unveiling sometime in the next few months.”

But some say the “technical problems” Kelly referenced with the prismatic glass didn’t lay with the type of glass, but rather with the fabricator.

Where Was the Mock-Up? Several companies contacted for this article wondered whether or not a full-scale mock-up of the 1 WTC podium wall had ever been produced. “I’m surprised they didn’t say ‘let’s make a full-size mock-up’,” says Bob Brown of Robert L Brown and Associates LLC. “A lot of times with something unique like this they make some full-sized prototypes. On very unusual jobs they do this pretty regularly.” John Barber, former president of Barber Glass Industries Inc., says when he was originally involved in development work for the project, and when he was told by a senior partner of SOM that if he met the price required he would receive a formal letter of intent, he developed a full-size panel. The sample he produced was 44 by 156 inches, which he says characterized the full panel which was to be 48 by 158 inches in size. “They never came to look at it,” says Barber. “I still have large samples in my office. Most importantly, we never received the letter of intent.” SOM did not respond to USGlass’ questions regarding whether or not a mock-up was produced. PPG’s Rob Struble says he doesn’t know if a mock-up was produced, but adds, “PPG recommends a mock-up on all commercial projects—it’s part of our standard design guidelines. However, where PPG sits in the contract chain, we can’t require it.”

Why It Won’t Work
Bob Brown of Robert L Brown and Associates LLC has been in the industry for 51 years and is well-known as a tempering expert. The industry consultant says he was contacted approximately a year ago by the “principals involved” when “they were experiencing problems fabricating the glass.

“The problems they experienced were breakage and in laminating it,” Brown says. “The panels were so deformed after tempering they couldn’t laminate it.” He explains why, to his knowledge, it wouldn’t work—no matter the fabricator.

Brown says the problem lies in taking 1-inch Starphire glass, in 160- by 48-inch panels, and putting it on a flat surface and “machining it.” In this case, the machining involves using an abrasive cutting device to create some pattern on the surface of the glass. The thick glass is also prone to spontaneous breakage during the tempering process, says Brown, who adds that heat-strengthened 1-inch-thick glass would present the same set of challenges.

“I have tempered 1-inch-thick glass,” says Brown. “The problem wasn’t heating it; the problem was waiting long enough for it to cool. That has to be closely controlled. If it cools too fast it gets too high of a stress level. Almost anything would cause it to rupture.

“You have major problems in ensuring the temper is stable after the surface deformation that occurs during and after tempering,” Brown continues. “You also have problems in meeting the stress limits. Even if you had the thin part of the glass meet those limits the thick part would exceed that.”

And even if the thick glass didn’t rupture during tempering, machining the glass would create a new set of problems.

“The machining would likely be done with industrial diamonds,” Brown says. “They may also be polishing those grooves. When they cut deep grooves they have created micro-fissures and the polishing is an attempt to minimize the damage. That is what consultants will tell you is causing a weak spot if you don’t get it nicely dressed around the cut. Those are micros-fissures or flaws on edges or surfaces.”

But he has other misgivings as well.

“My concern is how to put that glass on any holding device,” Brown says. “For holding or supporting the glass during the surface modification, the table or frame in which it is placed must be very level and stable [minimal flexure]. Large sheets of float glass weigh a great deal …. and though rigid at normal temperatures, it will flex under its own weight when not completely and fully supported. This would make machining the exposed surface an inaccurate procedure. If the machining is intended to create deep channels (grooves) in the glass surface, the variation in such grooving could cause uneven depths of grooves and subsequently cause a control problem for tempering in both the heating and cooling cycles. Such problems would be exposed with breakage, bowing and poorly tempered products.”

Brown is not the only one who has concerns about the use of prismatic glass on 1 WTC. Stanley Joehlin of the consulting company S.W. Joehlin Inc. is highly regarded in the industry for his tempering expertise and experience. In fact, he says, “Someone called me a few years ago when [Sanxin] got into trouble [on this job] and I said I wasn’t interested in going to China.” But he does have some thoughts on the prismatic glass option.

“Even if it would be possible to machine the glass and then polish the surface, without micro-cracks (which is next to impossible), you may be able to heat it uniformly if you left it in a very cool furnace,” says Joehlin. “However the longer heating time required can be expected to degrade the optical quality.”

“To temper a piece like that, I won’t say it can’t be done, but to uniformly heat and cool and keep it flat is almost beyond present technology—unless a company has a technique I am not aware of …. ”

Von Roenn Jr. agrees that the problem lies in the tempering.

“If someone can figure out how to temper it differently that would be wonderful,” he says. “I don’t know enough to say if that was possible or not. But when I first heard what they were trying to do [at 1 WTC] I never thought they could temper it successfully. You can strengthen the glass but you would never pass the necessary tests because the glass wouldn’t shatter in small enough pieces.”

Like Brown, Von Roenn Jr. says machining offers another set of problems. “There was no way they could ever have gotten a uniform tempering of the glass with the process of polished V-grooves,” he says.

Alternative Number One
For each person who says prismatic glass this thick can’t be made there are others who say emphatically that it can. At least two companies claim they have developed a process in which prismatic glass could be fabricated successfully. Both say they could have done it for 1 WTC—and both say they were in talks with SOM and the PANYNJ while Sanxin was attempting to fabricate the glass in China. One such company is a familiar name to those following the story.

Canada’s Barber Glass Industries was the company named in the original specification and spent millions in development work to create the prismatic glass. (For more on Barber’s initial involvement, see April 2009 USGlass, page 30.) It is important to note, however, that Barber Glass Industries’ fabrication arm is no more, as the 127-year-old company was placed into receivership on November 10, 2010. Former president John Barber’s wife, Susan, was successful in buying back the installation arm, and Barber himself assists in the management of the company. He also serves as a consultant for industry fabricators. Despite the widely known fact that he lacked access to a fabrication plant, Barber says he received a call in March 2011 from Nicole Driscoll at SOM who inquired again about Barber’s ability to fabricate the glass. Barber says he even went so far as to look for a plant and equipment to rent to fabricate the glass mock-ups.

Even before the call from Driscoll, Barber says he was aware that talks about choosing an alternative supplier had started again. In March 2011, Charles Flashburg of Johnson Screens told Barber that they were contacted via the parties involved as well. In the early stages of development, before the contract was awarded to Zetian, Barber was going to work with Johnson Screens, which would have provided the back-up screen that would hold the prismatic glass to the face of the building. (Johnson Screens did not return requests for comment at press time.)

“Both my company and Johnson Screens had an excellent grasp of the requirements and both had expended an excessive amount of capital to develop the product,” Barber says.

Why did SOM come back to Barber, years after the contract was awarded to Sanxin?

“I think the underlying reason is because I was only person with the complete knowledge who was able to manufacture the prismatic glass to their requirements,” he says.

In mid-2010, Barber fabricated prismatic glass with a similar profile to the 1 WTC glass for installation on the Sperone Westwater Gallery in New York City. Yes, the WTC is somewhat different, however the glass reacts quite similar in the fabrication and the tempering of the product, Barber says.

“The WTC required very tight tolerances and a minimal amount of visual support on the surface of the glass,” he says. “Sperone was a complete frame section supported fully around the perimeter, and the WTC was a frameless design. The large panels required for the WTC would be used to cover the mechanical section of the building for the bottom 20 floors and were purely decorative. Regardless of the size of the profile cut into the surface of the panel the issues in the product are similar.”

Barber adds that the prismatic glass would pose an additional learning curve in the 1 WTC installation because of the exposed edge, which would require extra care in the product’s handling and installation. He pointed out, however, that like any other product that is new on the market, it requires time and effort to work out all the installation and handling techniques.

Barber was willing to produce several full-size mock-ups for the PANYNJ as requested. He had proposed making four full-size panels and destroying two of them to demonstrate how the glass would react if broken or over-stressed. At that time, Barber gave SOM and the Port Authority a price of $796,000 to provide them with the required mock-ups.

“SOM was told not to continue its efforts on this design,” Barber says.

“I proposed that we could manufacture the prototypes in the timelines they required with no issues,” he says. “PPG was willing to provide me with the glass required. But let’s face it: With the current status of my company I don’t have a whole lot of bargaining chips.”

SOM may have been willing to take a chance, but Barber speculates it was the PANYNJ who “kiboshed” the idea. “I had lost my credibility in the eyes of many,” he says. “But, I’m still one of the most knowledgeable fabricators in the world.”

What about the concerns of consultants such as Brown regarding the tempering process?

“It all has to do with the tempering process,” agrees Barber “and [Sanxin] hadn’t figured out the cooling process. It is not tempered under a regular manufacturing process. At the end of the day we were able to temper it. Under a normal 19-mil tempering recipe you would heat the glass for 15 minutes—this product was cooked for 45 minutes, then cooled very strategically.”

Barber adds, “That’s where the magic happened. The glass stayed red hot for a period of time.”

Barber did create a full-sized panel early in 2009 during the initial development work (see box above to the left) but adds that since that time he had developed many improvements in the manufacturing of the product, many of which were made during the manufacture of the Westwater project.

“We improved the way we fabricated the glass involving the use of water to assist in the elimination of micro-fractures on the surface of the glass,” Barber says. Brown says the use of water or coolants could minimize the problem of micro-fissures or flaws on the edge of the glass.

“But it’s not just water—it’s the use of water along with the very sophisticated machine tools and numerous equipment modifications,” Barber adds. “Micro-fractures are a big issue in any fabrication of glass.”

The sun was streaming through the window, hit the glass and it was like rainbows everywhere and their jaws hit the floor. They loved it aesthetically, and it would also work structurally.
—Nathan Munz, Glassform

Alternative Number Two
Barber is not alone in his belief that prismatic glass is a viable option.

Several time zones away in Australia, another fabricator, Glassform, was perfecting a way to fabricate prismatic glass. The company was established in 1985 and Munz has 35 years of experience in the glass industry.

Munz says that Glassform, along with Barber Glass, was named as an approved fabricator for the prismatic glass in the original specification for the podium wall.

“We were named in the original specification and a gentleman at Tishman promised to put us in touch with the parties involved but we never heard and we went on with our lives,” Munz says.

Things changed in May 2010 when Munz says he received a call from a representative of Solera/DCM who was concerned about the Chinese fabricator’s inability to supply the prismatic glass.

“From my knowledge of how the glass was going to be fabricated, I knew there was no way that what they were doing would work,” Munz says.

But he was convinced his company could produce the glass, so he developed a new approach to fabricating glass that would satisfy the aesthetic requirements that architect David Childs had designed—including the ability to generate rainbows.

“In order to produce the glass that was designed by Childs for 1 WTC, we needed to produce a quality of flatness without ripples,” Munz says. “The zigzag shape has to have a certain quality. Our sample shows our glass is a true prismatic glass.”

To produce the sample Munz says he used PPG Starphire glass that he had in his plant. He adds that Glassform’s solution for the prismatic glass does not require 1-inch-thick glass to be used, so the sample used a thinner PPG Starphire glass.

So how does Glassform’s method overcome the challenges pointed out by experts?

“I learned that the Chinese were machining the glass with a peripheral V-shaped wheel that will leave ripples on the glass surface,” Munz says. “You cannot get a splay of color without very flat surfaces on the prism.” He explains that the V is the shape of the edge of the wheel, which grinds the surface to form the V in the glass, but that his method uses a different type of wheel.

“The reason our prismatic glass has a surface finish that is flat and without any ripples is indeed the method of machining used. I believe that all other attempts involved machining the glass in a manner that could never achieve the necessary finish to generate rainbows from sunlight—in David Childs’ words, ‘splays of color.’”

In addition, Munz says Glassform’s design solution avoids the tempering and laminating problems arising from other approaches, which are likely to have prevented the successful fabrication of the final product.

Munz is keeping additional information about the product proprietary, saying only that Glassform “figured out how to manufacture prismatic glass panels with the aesthetic and structural properties necessary to satisfy the requirements of SOM’s design for the 1 WTC façade.”

A Jaw-Dropping Meeting
Two months after the phone call from DCM/Solera, on July 23, 2010, Munz traveled to New York City with a sample. Confident he could produce the desired glass, he was ready to meet with representatives from Tishman, SOM, DCM/Solera and the Port Authority—but the meeting never took place.

Munz wanted all the parties to sign a confidentiality agreement and says only DCM/Solera would comply. So he went back to Australia, but didn’t give up hope and went to work on another sample—this one 4 by 2 feet in size. He flew back to New York City in October 2010 but this time, he says, neither Tishman nor SOM would meet with him.

Munz says the project manager, Ken Lewis, eventually agreed to meet. Also present, Munz says, were key members of the design team. Munz did not request the signing of a confidentiality agreement at this meeting as he had already submitted a patent application to the U.S. Patent and Trademark Office.

“The sun was streaming through the window, hit the glass and it was like rainbows everywhere and their jaws hit the floor,” Munz recalls. “They loved it aesthetically, and it would also work structurally.”

Munz says he was asked to leave the sample so it could be shown to others and he complied. “When I came back the following week to confirm a second meeting as agreed at the end of the previous meeting they stone-walled,” Munz says. “Subsequently a meeting with the design team was arranged on the basis that it was not for the purposes of 1 WTC but to discuss potential uses of the Glassform prismatic solution in other future SOM projects.”

And what about that sample? “It was shown to other SOM architects, and the written feedback I received [privately] from one was, ‘This is the best sample that has ever been produced for this installation. Everyone I spoke to here agreed … Since this sample proved to be so beautiful, it would seem that quite a few people are uncomfortable with how this situation has evolved.’ ”

And at least one other person saw the Glassform solution as a valid one. Leon Jacob, glass consultant with Jacob & Associates Pty. Ltd., based in Sydney, Australia, says he was engaged as a consultant by the PANYNJ to undertake specific tasks related to the prismatic glass façade of 1 WTC.

“I am bound by confidentiality not to disclose details of my engagement,” he says. “I can, however, comment that, after it became evident that the contracted source of the prismatic glass panels was unable to supply, I advised Tishman Construction and SOM Architects that I was aware of the Glassform solution for the fabrication of the prismatic glass and that I believed it was the only solution available which satisfied the aesthetic and the structural requirements, and was able to be fabricated and supplied.”

Placing Blame,Money Wasted
Though Tishman Construction has remained relatively quiet on these issues both Barber and Munz contend Tishman did not facilitate constructive communication on the project.

“Tishman was controlling the process and blocked access at every point,” Munz says. “They didn’t want Glassform’s prismatic glass considered and they blocked access to the architect.”

“From day one there was resistance from Tishman that we did not understand,” adds Barber. A representative from Tishman Construction declined to comment on the story.

But some say there is plenty of blame to go around. When Munz learned in early April 2011 that the Chinese were definitely out, he sent a letter to Steve Plate, director of the 1 WTC Construction for the PANYNJ, and summarized nine key points.

Among them was the fact that he traveled to New York in July 2010 to present his solution together with samples. “The consensus at SOM was that the sample viewed ‘was the best that has ever been produced for this installation,’ said the letter Munz sent to Plate. “SOM was scheduled to meet a second time after a few days, but when this arrangement was to be confirmed, they advised that they did not want to proceed with the second meeting. It appears that a third party had instructed them not to consider any proposal from Glassform.”

The letter, dated April 4, 2011, also stated: “It appears that the prismatic concept for the 1 WTC podium façade is now being abandoned on the grounds that it is not able to be supplied. This is simply untrue.”

According to Munz, when Plate received the letter he instructed a representative of Tishman to call Munz on behalf of the Port Authority to say: “The owners have decided to abandon the prismatic glass concept for the 1 WTC façade.”

Since the parties aren’t revealing why prismatic glass was abandoned many have drawn their own conclusions—and most of those have to do with cost.

“My first guess is the cost concern,” Brown says. “I’m referring to Donald Trump’s concept of going to China because ‘it’s cheaper there than it is here’” (see November 2010 USGlass, page 42).

Ten million dollars had already been spent on the prismatic glass portion of the project. PPG’s Rob Struble also confirms that PPG did produce the specified Starphire glass, some of which was shipped to China and the remainder of which is sitting in a warehouse.

“It is a shame they spent that much money without testing it first,” von Roenn says.

Consider Kelly’s earlier comment: “As design moved to the testing phase, it became clear that the prismatic glass simply had too many technical problems to overcome and at a budget that was not cost-effective.” But Munz says he could have produced the glass cost-effectively.

“We can use any glass,” he says. “One of the differences in our approach is we don’t need glass that runs thick. We could use ½-inch-thick and that reduces costs.”

Barber can’t help but think what would have happened if the parties involved had used his company as the original fabricator.
“They had their sights set on saving money,” says Barber. “I was told $8 million was the number we had to sharpen our pencil on. So now two years and millions of dollars later, we are left with a total redesign and a stock of 1-inch glass that will never be used. How much did they save? They put their trust in a company that could not make the product.”

“They can’t afford to have any more egg on their face,” Brown adds. “From that standpoint, they can’t afford to do it.”

"To temper a piece like that, I won’t say it can’t be done, but to uniformly heat and cool and keep it flat is almost beyond present technology. Unless a company has a technique I am not aware of …."
—Stanley Joehlin, glass consultant

What’s Next for Prismatic Glass?z
While it seems prismatic glass won’t be used on 1 WTC, will it be used in similar projects in the future? Can fabricators overcome the technical problems?

Brown gave a litany of reasons the prismatic glass wouldn’t work due to tempering and machining problems. That being said, he sees one way the prismatic glass could be a workable solution for future projects.

“If a company is using chemical tempering, then laminating, it could work,” he says. “It would be a costly process and a patience-testing process,” and one, he added, that only might possibly work over a cycle of multiple hours.

While Joehlin doesn’t claim to be a chemical tempering expert, he says chemical tempering doesn’t offer the right break patterns that are needed to create a safety break pattern for prismatic glass.

“It’s the high central tension that is used to produce the break pattern,” he says. “If you had a piece like that shatter in a storm I don’t know how it would break.”

And if it did work he says there are other difficulties at play. “With that variation in the thickness of the glass, I don’t know of anyone in the world that has a chemically tempered tank close to the size that would be needed.”

Barber says chemical tempering is not a good option.

“This process alters the molecular movement in the surface of glass,” he says. “The chemical process can be easily destroyed, and would not lend itself to this type of install. We entertained the idea right from the beginning but once we investigated it further we never pursued it.”

Munz remains mum on whether or not he uses chemical tempering in his process. “As I previously advised, we prefer not to publish details of our solution at this time,” he says.

Others say they would have used a completely different solution.

“We would have laminated prismatic glass using a technique we have called Prismalite,” von Roenne says. “This is a name we use to describe our technique for laminating prismatic glass pieces to plate glass. It is typically used for applications that have natural light so that the prisms break up the light into spectral colors.”

While representatives of fabrication companies talk about how they “would have done it,” Brown says he’s glad he didn’t have to attempt it.

“I’m sure glad I didn’t have to do it,” he says. “Someone [plural] overreached in trying to make fully tempered panels of this shape and surface configuration.”

But Munz says he is absolutely certain this glass will be installed on other buildings and he is now making large-scale samples. He also is talking to architects in Australia to use the product on a smaller scale.

“Just a few architects are aware of it,” Munz says. “Early next year I will have a supply available … There is no question in my mind we could have supplied it to 1 WTC on time.

“Every time it goes up on a building people will say ‘that could have been on 1 WTC,’” he says.

Jacob adds, “I think the concept was brilliant and it could have been a magical building in terms of Childs’ approach and they could have had it.”

Tara Taffera is a contributing editor for USGlass magazine. She can be reached at ttaffera@glass.com or follow her on Twitter @dwmmag.

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