Abstract: The disclosed method minimizes the tendency of sodium polyborate (the chemical compound obtained from boric acid and sodium sulfate) to set up into a plaster of Paris-like mass during the reaction of concentrated sulfuric acid and a hydrate of sodium tetraborate. By adding a relatively small amount of talc at an early stage in the process of making sodium polyborate, the amount of shear force needed to break up the sodium polyborate product into small particles is greatly decreased. The resulting dry, free-flowing, finely-divided product is useful as, among other things, a pesticide and a fire-retardant agent.