He returned to America, struggled professionally for 13 years as a chemistry instructor, then in 1899 took a position as an industrial chemist with the New Jersey Zinc Company. Reese soon attracted the attention of DuPont executives J. Amory Haskell and Hamilton Barksdale, who were seeking an able manager to organize and head a new explosives research laboratory. In 1902 they named Reese as the first director of Eastern Laboratory, one of the country's first pioneering industrial research laboratories.
In the following years, Reese built a first-class research organization and spearheaded the development of low-freezing dynamites and "permissible" explosives for use in combustible mining environments. Reese's success at Eastern Laboratory led to his appointment as the first director of DuPont's new Chemical Department in 1911, where he worked diligently to centralize the company's several research operations. In 1917 he was elected to DuPont's Board of Directors. After World War I, Reese's centralized research structure failed to meet the needs of the company's expanding, diversified businesses, and in 1921 a company-wide reorganization authorized those businesses to establish their own research labs using Chemical Department personnel. Reese remained the nominal director of what remained of the centralized Chemical Department until his retirement in 1924. He continued working as a chemical consultant at DuPont until 1930, and remained on the company's Board of Directors until his death in 1940.
As the DuPont Company expanded beyond black powder into dynamite production at the end of the 19th century, it recognized the need for a full-time research facility dedicated to studying and improving explosives. In July 1902 it opened the Eastern Laboratory at its Repauno dynamite plant in Gibbstown, N.J., and appointed Charles Reese as its first director. The lab was named for the Eastern Dynamite Company, then a holding company for DuPont's dynamite businesses, and employed 10 researchers. It was DuPont's first formally organized laboratory, and was the first industrial chemical research lab established in the United States. DuPont's opening of another research lab, the Experimental Station, in the following year (1903) helped define the company's dual approach to research: applied research aimed directly at new or improved products, such as Eastern conducted, and the Experimental Station's basic or fundamental research aimed at new knowledge.
In 1907 Eastern Laboratory developed the first successful low-freezing dynamites, as well as a number of permissibles, explosives approved for use in gaseous and dusty mines. During World War I, Eastern conducted DuPont's initial efforts to research and produce dyes in order to replace German imports cut off by the British naval blockade. In 1918 dyestuffs research moved into the company's new Jackson Laboratory at Deepwater, N.J., and Eastern concentrated on explosives research for the war effort. After World War I, Eastern's research diversified beyond explosives into such areas as developing effective process technology for tetraethyl lead gasoline additives, and improving DuPont's many chemical manufacturing operations. Eastern also helped develop ingredients and processes for making Dacron polyester in the 1950s.
By its 50th anniversary in 1952 Eastern had grown to 100 separate buildings on a 300-acre site. After DuPont discontinued dynamite production at Repauno in 1954, Eastern Laboratory researchers developed high-pressure technologies for making industrial diamonds from graphite, and for bonding metals such as the copper-cupronickel slab from which the first U.S. dime and quarter sandwich coins were made. DuPont phased out the Eastern Laboratory in 1972, and its operations and personnel were transferred to other company facilities.