The aim is to probe the micellar compositions of fluorocarbon/ hydrocarbon mixtures used in commercial fire-fighting foam formulations (Figure 1) using contrast variation SANS. These fluorocarbon surfactants have already been studied individually and as F/F-surfactant mixed systems (Figure 1) and now will be studied as F/ H-surfactant mixtures within a typical range of compositions commensurate with a fire-fighting formulation. The data will allow us to understand how the surfactant aggregation is affected by mixing to provide new understanding on the colloidal properties of these practical surfactants. This is the third stage in a new 3-year program, including SANS, so that F-carbon surfactants can be replaced by more environmentally-responsive low-F or hydrocarbon analogues. Chris Hill is a 3rd year PhD student fully funded by fire-fighting technology company Angus Fire.