From “I. M. Pei: Life Is Architecture,” a beautifully designed new volume by Shirley Surya and Aric Chen, a story of insistence driving invention:

Wary of the greenish tint characteristic of commercially available glass, Pei insisted on using a completely clear alternative for the Louvre’s pyramid. Along with President Mitterrand’s intervention, this led France’s largest glass manufacturer, Saint-Gobain, to devise an entirely new production process for large-scale manufacturing. Beginning by sourcing pure white sand from Fontainebleau, Saint-Gobain proceeded to develop a specialised furnace that reduces the amount of the naturally occurring iron oxide in the glass formula, eliminating the source of the green hue. The 675 diamond and 118 triangular panes were transported to a factory in the United Kingdom that was able to polish their surfaces to perfect planarity, achieving flawless results with optical properties close to those of crystal. (Photo)