The Ames process was used on August 3, 1942, by a group of chemists led by Frank Spedding and Harley Wilhelm at the Ames Laboratory as part of the Manhattan Project. It is a type of thermite-based purification, which was patented in 1895 by German chemist Hans Goldschmidt. Development of the Ames process came at a time of increased research into mass uranium-metal production. The desire for increased production was motivated by a fear of Nazi Germany's developing nuclear weapons before the Allies. The process originally involved mixing powdered uranium tetrafluoride and powdered magnesium together. This mixture was placed inside an iron pipe that was welded shut on one side and capped shut on another side. This container, called a "bomb" by Spedding, was placed into a furnace. When heated to a temperature of , the contents of the container reacted violently, leaving a 35-gram ingot of pure uranium metal. The process was quickly scaled up; by October 1942 the "Ames Project" was producing metal at a rate of  per week. The uranium tetrafluoride and magnesium were sealed in a refractory-lined reactor vessel, still referred to as a "bomb". The thermite reaction was initiated by furnace heating the assembly to ; the large difference in density between slag and metal allowed complete separation in the liquid state, yielding slag-free metal. By July 1943, the production rate exceeded  of uranium metal per month.  Approximately 1000 tons of uranium ingots were produced at Ames before the process was transferred to industry.
The Ames project received the Army-Navy "E" Award for Excellence in Production on October 12, 1945, signifying 2.5 years of excellence in industrial production of metallic uranium as a vital war material. Iowa State University is unique among educational institutions to have received this award for outstanding service, an honor normally given to industry.