Abstract The glass forming range of alkali borates has been extended to R = 5.0 (83 mol% alkali oxide) using a solution method. This method involves the reaction between solutions of boric acid (H 3BO 3) and alkali hydroxide (MOH). Physical properties and NMR studies were performed on the intermediate and final glass products of this method. We have obtained results for the entire alkali borate system including lithium, sodium, potassium, rubidium and cesium. The structure of these invert glasses remains enigmatic.