Nanoporous membranes fabricated by polymerization around soluble templates have found many applications in (bio)sensors, charge storage devices, filtration and catalysis. However, we are currently developing two distinct novel applications: functionalised membranes for nucleotide and protein ¿blotting¿ matrices and latent fingerprint enhancing coatings. When making membranes using these methods, characterisation of the subsurface cavities formed is notoriously difficult. For small motifs, specular NR can measure changes in overall solvation, but for applications such as those above, where the cavity size is of the order 50-400 nm, SERGIS and SESANS are appropriate. Here we seek to make the first measurements of these types to probe the number density and size of cavities generated in a templated electrodeposited polymer, thereby adding quantification to the cartoon depictions often used.