Franks had a substantial personal fortune, which he used to build up some remarkable personal collections in parallel with his museum work on acquisitions. Though this activity was as an independent collector, it was of benefit also to the holdings of the British Museum, either in the short or longer term. It was largely devoted to the collection of ceramics and precious objects of medieval art; it also included many items from the Oxus Treasure, and Franks built up that side of his collection through dealers in India and by purchase from Alexander Cunningham.