Amorphous boric oxide-containing product having about 80 to 90% B2O3 is produced by heating boric acid to an elevated temperature of about 180 DEG to 220 DEG C. to dehydrate the boric acid and form a molten glass which is cooled to a solid glassy product. The solid glass can be comminuted to produce a particulate product. Preferably the boric acid is heated at about 195 DEG to 205 DEG C. The process is readily adapted to a continuous process in which the boric acid is continuously fed through a heated reactor-mixer such as a Kneadermaster mixer or Discotherm mixer. The molten glassy product is cooled to form a solid glassy product which can be comminuted to a desirable particle size range.