Physical developer (PD) is a latent fingerprint development technique that is highly effective on paper and related surfaces, notably banknotes. The process exploits a redox reaction in which Ag(I) ions in solution are reduced by Fe(II), resulting in deposition of metallic silver on fingerprint residue on the surface. The standard formulation includes a cationic surfactant, whose presence is critical to formulation stability and efficacy, but whose role is poorly understood. By analogy with additives used in electrodeposition processes, surfactant adsorption can be expected to play a significant role. Here, we seek to determine the extent and composition of the surfactant layer on a silver surface using specular neutron reflectivity. Contrast variation of both solvent and surfactant will be exploited. The outcomes will guide optimization of the PD and derivative processes.