During World War I, Dow Chemical supplied many war materials the United States had previously imported from Germany. Dow produced magnesium for incendiary flares, monochlorobenzene and phenol for explosives, and bromine for medicines and tear gas. By 1918, 90 percent of Dow Chemical production was geared towards the war effort. At this time, Dow created the diamond logo that is still used by the company. After the war, Dow continued research in magnesium, and developed refined automobile pistons that produced more speed and better fuel efficiency. The Dowmetal pistons were used heavily in racing vehicles, and the 1921 winner of the Indianapolis 500 used the Dowmetal pistons in his vehicle.