The Outer Membrane (OM) is found in bacteria which cause plague, cholera & Legionnaires disease. It is important as; a barrier to antibiotics & the site of human-bacteria interaction. However bacteria are too small to allow us to do precise measurements of the structure and dynamics of this critical interface. Using neutrons as our eyes we have recently investigated OM models which imitate many aspects of the natural OM. This includes its structure where the outer surface is dominated by a molecule called lipopolysaccharide (LPS). However the model is unstable if we use the very large versions of LPS found in some bacteria. This project aims to understand this by varying the ions that are known to stabilise the OM. In this way we seek to understand what maintains the structure of the natural OM and thus improve our future models.