Abstract: This thesis seeks to explore the development of a building material with regards to its durability and production. It does so in the examination of the advances in material understanding and technique with regards to a unique twentieth century material – precast exposed aggregate concrete. Tested, refined and later patented by craftsman John J. Earley, the precise process of creating exposed aggregate concrete cladding (today known as the MoSai technique) holds unique implications for its preservation. Analyzing what Earley - and those who helped refine the MoSai process over the years - understood with regards to the material's properties will determine whether the material's evolved production has preservation implications inherent to the process. The way in which Earley approached perfecting precast exposed aggregate concrete paneling will also assert his place in architectural history beyond the development of a durable, permanent material; his Earley Process has had lasting influences on today's standards and production – separating today's materials from their traditional predecessors and thus, potentially affecting how preservationists view all modern materials as they ready themselves for the future of their work.