New detergents will increasingly rely on sustainable products and the use of enzymes will become ever more important. However, the process of destruction of stains (often proteinaceous) by enzymes and the removal of residues from the surface is a complex process. We propose to use proteins as model stains and follow directly their destruction by a protease by neutron reflection with and without added surfactant. This should (a) give insights into the molecular process of cleaning and (b) give fundamental information about interfacial enzyme kinetics. We will use the well characterized enzyme, Savinase, and supported model layers of BSA denatured at a hydrophobic surface (OTS on silicon). Previous studies at the hydrophilic surface have shown that surfactant swells the BSA layer which, combined with the already denatured surface, may assist access of the layer to the attacking enzyme.