Chemical enhancement of soil-based marks on nonporous surfaces followed by gelatin lifting

This study assessed the use of processing techniques (potassium thiocyanate, 2-2-dipyridil, potassium ferrocyanide, ammonium pyrrolidinedithiocarbamate, safranin, magnetic powder) for the enhancement of soil-based marks on nonporous surfaces, followed by gelatin lifting for the recovery of these marks. Other variables in the study included the use of nonporous substrates with varying colors (ceramic tiles, glass, linoleum, plastic bags, leaflets) and different aging periods (1, 7, 14, and 28 days) prior to enhancement and gelatin lifting. A numerical grading system from -1 (deterioration) to 4 (recovery of all fine detail) was adopted to assess the quality of the enhancement achieved. In this study, the two most effective chemical enhancement techniques for soil-based marks on nonporous surfaces were safranin and potassium thiocyanate, specifically on grey linoleum and white ceramic tiles. One-day aging of soil-based marks provided poor results, whereas 28-day aging periods provided superior enhancement. In general, lifting with gelatin lifts provided further improvement on the initial enhancement, by means of contrast and sharpness. However, the use of gelatin lifting sometimes resulted in the deterioration of the original mark. Marks treated with safranin and lifted with white gelatin lifts provided even further improvement through fluorescence examination.