The United States Navy continued filling armour-piercing shells with explosive D after some other nations had switched to TNT, but began filling naval mines, bombs, depth charges, and torpedo warheads with burster charges of crude "grade B" TNT with the color of brown sugar and requiring an explosive booster charge of granular crystallized "grade A" TNT for detonation. High-explosive shells were filled with "grade A" TNT, which became preferred for other uses as industrial chemical capacity became available for removing xylene and similar hydrocarbons from the toluene feedstock and other nitrotoluene isomer byproducts from the nitrating reactions.