More than fifty years ago, Thomas A. Edison turned his inventive genius to the problem of monolithic concrete, and became a pioneer in the field of prefabricated housing. The plan was patented on December 22, 1908, and during the following months Edison designed a series of complex molds which would serve as forms for his concrete houses. A New York firm of architects, utilizing Edison's sketches, drew up the detailed plans. Basic to the plans were Edison's ingeniously conceived cast-iron molds, which when assembled would produce in a single operation walls, floors, stairways, roof, bath and laundry tubs, and conduits for electric and water service. As many as 500 different sectional molds were required for a single unit. Moreover, because of the intricate tracery being attempted, each mold had to be faced with nickel or brass. The cost per set of molds soared to $25,000. Nevertheless, since each set of molds could be re-used indefinitely, Edison estimated the cost per house unit at $1,200, including plumbing, heating, and lighting fixtures. A second problem was that of a concrete mix design. Wooden forms were constructed at Edison's West Orange, New Jersey, lab and a series of tests were conducted to determine the influence of gravity upon the heavier materials such as crushed stone and sand. To overcome the tendency toward segregation during placing, Edison devised an additive. This jelly-like colloid produced a mix which was free-flowing, yet which formed a uniform mass throughout, leaving the surface smooth and reportedly waterproof. Despite Edison's dedication, his monolithic concrete homes never became popular. Perhaps because he was too far ahead of his contemporaries, Edison's "concrete dream" was destined to gather dust for these many years.