Latent fingerprints on a porous substrate such as paper are developed for viewing and recordal by applying heat to cause the fingerprint to be clearly viewed under radiation to cause the fingerprint to fluorescence (e.g. a few seconds heating with hot air or client contact with a heated device at around 260° C.) and viewing under e.g. light of 200 nm to 550 nm with a filter in the yellow to orange wavelength region. Alternatively more extended heating can render the fingerprint assemble under ultraviolet light, and under yet more extended heating permits viewing under white light.