The impact of alternative surfactants on the performance of physical developer formulations

Physical developer (PD) is a physicochemical detection technique for fingermarks on porous surfaces. One of the surfactants in PD, Synperonic® N, has been phased out of manufacture due to generating environmentally harmful degradation products. Previous research, mainly in the US, the UK, and Europe, has attempted to trial alternatives to Synperonic® N, such as Tween® 20 and DGME, however little comparative work has taken place in an Australian context. Over 3000 fingermarks were developed and evaluated to compare three alternative PD formulations containing Synperonic® N, Tween® 20, and DGME surfactants. Their performance was examined across a range of donors, depletions, substrates, and fingermark ages. Formulation performance was comparatively graded using the University of Canberra scale, with overall quality also assessed using a modified Centre for Applied Science and Technology (CAST) scale. A pseudo-operational trial was undertaken on documents from the 1950s to the 1980s. Of the three alternatives, the Tween® 20 formulation performed best, producing three times as many fingermarks than the Synperonic® N formulation graded a CAST ‘4’, and five times as many than the DGME formulation. It was concluded that Tween® 20 is a suitable replacement surfactant for Synperonic® N in PD. Validating a formulation that performed equal to or better than the Synperonic® N solution is a positive outcome, not only in consolidating a gap in the literature more broadly, but also practically for use in Australian casework, given the environmental harm caused by Synperonic® N and the depleting stocks that remain.