<p>Currently zircon-based slurries dominate the steel investment casting industry. Zircon’s thermal expansion and high thermal conductivity make it more suitable for higher melting point alloys, such as steel. However, the price of zircon flour has doubled in the past decade, and an alternative has been desired in the investment casting industry. At the University of Northern Iowa, an alternative mullite-based slurry system was evaluated and compared to a conventional zircon-based slurry system. A series of testing including establishment of control parameters, shell building, pattern removal, and casting trials were conducted to compare the performance of these two slurries for steel casting applications.</p>