 The glass was custom @-@ made at a factory in Mount Pleasant , Pennsylvania , and shipped to the structural glass panel manufacturer in Melbourne , Florida . The panels were then shipped by truck to Chicago . The glass is white glass , rather than the usual green glass that results from iron impurities . This has the <unk> of increased image clarity , but greater dirt visibility . Each block is 5 by 10 by 2 inches ( 127 by 254 by 51 mm ) with glass thin enough to avoid image distortion . On each block , one of the six faces is polished , and the other five surfaces are textured . 
