A new method for improvement of 1,2-indandione-treated latent fingermarks on thermal paper will be described in this paper. Treatment with conventional techniques like ninhydrin in petroleum ether or DFO solution produces a black color on the thermosensitive side of thermal paper. The new method using 5,6-dimethoxy-1,2-indandione with polyvinyl pyrrolidone (PVP) can reduce this dark staining without removing the thermosensitive layer and parts of the developed fingermarks. An advantage of this method is that the developed fluorescent fingermarks appear in sharp lines and high contrast . The developed fingermarks can be observed when excited in the 535 nm region and using an orange-red goggles. There is no background coloration in this method. In addition, some tests were performed, leading to an optimized working solution, which charges the paper with a minimum of chemicals, is cheap, and enables a large quantity of papers to be treated in a short time and without involving any pre- or post treatment.
Keywords: 5,6-Dimethoxy-1,2-indandione; Polyvinylpyrrolidones; Thermal paper; Latent fingerprint