UK: cracks in “gherkin” may be glass cancer

Cracks appearing in toughened glass panels on the so-called “gherkin”, the landmark building nearing completion in the City of London, may be due to “glass cancer”. The building is a high profile proj…

Cracks appearing in toughened glass panels on the so-called “gherkin”, the landmark building nearing completion in the City of London, may be due to “glass cancer”. The building is a high profile project designed by world renowned architect Sir Norman Foster. So far 25 panels out of over 5,000 need replacing. Although the most likely cause of the cracks is damage in transit or variations in weather conditions, glass cancer, which was responsible for cracks in the roof of another landmark London building, the Eurostar terminal at Waterloo station, cannot be excluded. The phenomenon is due to the formation of nickel sulphide crystals in toughened glass during manufacture. The crystal can exist in two sizes depending on the temperature of the glass. When the glass is made the crystals assume the smaller size but in time they expand to the larger size, causing cracks. Replacing the panels on the “gherkin” is set to take up to eight weeks but should not result in a postponement to the mid-December opening date.