Mica is an exceptionally important mineral in surface science. The understanding of the surface chemistry underpins many commercially important processes. Academically, mica is the substrate of choice in many other techniques from Atomic Force Microscopy to Surface Force Apparatus. We have recently been successful in measuring the mica water interface with neutron reflection measurements; a challenging goal in itself. Here we wish to continue our investigation of this important interface by studying the adsorption and desorption of didodecyldimethylammonium bromide (DiDAB) at the mica water interface, following our very preliminary investigation that revealed some unexpected behaviour.