Remember how I said that I wanted to know more about the material being used by Norman Foster in the Astana tent project in Kazakhstan? Well, I took the extraordinary step of looking it up. Turns out that the material is called ETFE (Ethylene Tetrafluoroethylene). It has been used in some other similar applications around the world - notably the Eden Project and a few sports stadiums. Evidently it is very lightweight and relatively strong, making it a good material where the transparency of glass is needed, but weight is an issue. People also use this material in the creation of greenhouses.