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The Milan "Borsa" Cathedral Glass ellipse dome protected by new roof of laminated glass

Cathedral glass is protected by a roof of glass laminated with DuPont Spallshield®

The Milan "Borsa" or Stock Exchange, built in 1932, is one of the city's most impressive buildings. The key to its success is a 30 x 20 metre, yellow and violet, Cathedral Glass ellipse dome crowning the roof of the Borsa's three-story, internal atrium. For many years, however, safety and security concerns had required the magnificent ellipse dome to be protected by an outerwire, glass roof – until architects from Studio Architetti BBPR,Milan came up with the idea of shielding the Cathedral glass from the elements using an outer, protective roof of glass laminated with DuPont Spallshield^® .

Use of Spallshield^® , a composite of PVB and an abrasion-resistant polymer, instead of standard laminated glass meant that one lite of glass could be used instead of two, reducing the overall weight of the structure but still giving the outer roof the full properties of laminated glass. What's more, protection was far greater than from the previous, outer-wire, glass roof – as an early incident proved.

One of Studio Architetti BBPR's project architects, Sergio Fumagalli, explained: "Italian code (the 'Norma Uni') mandates that security glass must withstand a rigorous testing procedure which includes 30 blows from a club. However, in the case of the Borsa dome, we had an unintended but impressive demonstration of its protective qualities when a large piece of metal scaffolding pipe fell onto the outer glass 'tent' ".

"We held our breath as the glass broke but the tough, resilient Spallshield^® held, protecting the fragile Cathedral glass beneath," Fumagalli added.