The structure of insoluble monolayers of surfactant material at the air-water interface, known as Langmuir-Blodgett monolayers, are of importance both technologically and biologically . However, it is only in the past approximately 30 years, that a non-destructive, quantitative probe of these systems has been developed . Where previously surface pressure-surface area isotherms and indirect methods, such as surface potential measurements, are applied, neutron and X-ray reflectometry and Brewster angle microscopy can offer a more direct, structural, description. The use of reflectometry methods to study the structure of Langmuir-Blodgett surfactant films was first published by and was then popularised through subsequent work .