Latent fingerprints are valuable pieces of evidence that are often found when a crime has been
committed. This type of evidence is hardly visible so the application of techniques to make it more visible is
necessary. Furthermore, latent fingerprints can be found in wet environments, and these surfaces can be wet by
water from several sources that differ in their pH and particulate matter, such as rain, roadside, canal or sea
water. Small Particle Reagent (SPR) is an advantageous technique for latent fingerprint detection on wet
surfaces. In this study, surface samples were moistened by soaking in various solutions to represent water from
different sources. Eleven formulae of SPR, three (SPR I, II, III) from the published references and eight new
modified ones, were investigated to evaluate the optimal formula for latent fingerprint detection on wet nonporous
surfaces. The best quality of developed latent print was obtained from the SPR containing molybdenum
disulfide in tergitol NP-7 and choline chloride. However, on a dark surface, the best quality was obtained from a
suspension containing zinc carbonate as small particles. The soaking solutions used in this study did not affect
the effectiveness of SPR. Nevertheless, the salt solution affected the fingerprint impression.