The intricate and delicately beautiful Baha'i Temple in Wilmette, Illinois, demonstrates the durable versatility of concrete. The temple's exquisite symmetry and delicate tracery become all the more amazing when you learn that its surface is exposed aggregate concrete. New York architect Louis Bourgeois prepared full size layouts of the intricate segments of the dome and the nine great ribs that divided them, sketching his pattern of intertwined tendrils, flowers, leaves, and fruit. On the dome he represented the orbits of stars and planets in a flowing pattern of ovals, circles and curves. The end result was one of the most intricate architectural patterns ever conceived.
The architect had wanted the building and especially its great dome to be as white as possible, but not with a dull and chalky appearance. To achieve the desired effect, he proposed an opaque white quartz found in South Carolina to reflect light from its broken face. This would be combined with a small amount of translucent quartz to provide brilliance and life. Puerto Rican sand and white Portland cement were added to create a combination that reflected light and imparted a bright glow to the concrete surface.
After nearly 50 years of weathering, by far the greater part of the intricate surface of this immense building is in perfect condition. In 1970 the surface was cleaned to remove the effects of polluted air, restoring the surface to its gleaming white. A methyl methacrylate coating was then applied to further protect the surface.