Latent fingerprints are not often left in heterogeneous or protected environments, so there is the need to be able to detect their presence on different surfaces and after they have undergone the action of atmospheric agents or have been found, for example, on objects soaking in water of different types of impurities and sediments. Small particle reagent (SPR) is a physical development technique for fingerprint detection on wet or moist surfaces.(1) There are many formulae of SPR available nowadays but the optimal formula has never been reported. In this study, the best SPR- formula for detecting latent fingerprints on wet non- porous surfaces was demonstrated.