Hydrolysis of boron is investigated as a part of a boron/boron oxide solar, water-splitting, thermochemical cycle. Boron was hydrolysed and boron oxide was gasified with steam in a tubular reactor. The influence of the reactor temperature and time on hydrogen conversion was measured at furnace set point temperatures of 873, 973 and 1073 K. The hydrogen production rate was measured by inline gas chromatography. The products were analyzed by X-ray diffraction. The average hydrogen production efficiency of 92% was obtained for both 973 and 1073 K. The formation of a boric acid layer on the reactor walls was attributed to the gasification of the boron oxide. The X-ray analysis shows 100% conversion of the boron to boron oxide and boric acid.