BslA is a globular protein that has recently been shown to play an important role in developing the morphology and hydrophobic properties of Bacillus subtilis biofilms. A molecular understanding of the role of BslA will be valuable in efforts to disrupt biofilm formation and BslA itself could find application as an emulsion stabiliser in the food industry. In vitro, BslA quickly forms an elastic layer at the air-water interface. Very little is currently known about the structure, thickness and density of such layers. We propose to perform kinetic measurements of deuterated and undeuterated wildtype and mutant (L77K) BslA film formation at an air-null reflecting water interface and measure the thickness and surface excess of fully formed films. Further, we will determine the relative position of wildtype BslA and L77K at an air-D2O interface.