In 1714, the Dutch scholar Willem Jacob's Gravesande published a theoretical essay on how to optimize the air-pump. Although his paper did not attract much attention, there was one important supplier of air-pumps who knew about it: the Leiden instrument maker Jan van Musschenbroek. 's Gravesande and he cooperated intensively between 1717 and 1742. Among other things, this cooperation resulted in two new air-pump designs to replace Musschenbroek's own models. A closer analysis of's Gravesande's influence on Musschenbroek's repertoire reveals that (...) the various changes were not inspired by the theory of the air-pump. Commercial and practical considerations were much more important than theoretical reflections, even though both approaches aimed at the same goal: a fast and handy air-pump. (shrink)