Differentiation of inks on documents by dequenching of ultraviolet fluorescence: A case report

Detection of chemical erasure and differentiation of inks by examination under long- and short-wave ultraviolet light generally solves many Questioned Documents problems. Many dyestuff-based inks fluoresce when examined under ultraviolet light, when the dye component fluoresces under the direct ultraviolet light. Sometimes, however, this fluorescence becomes quenched when the dye becomes bonded to some other, non-fluorescent compound, and does not fluoresce under ultraviolet rays. When the dye is freed from its bonded state it regains its fluorescence.In a recent case, two specimens of writing in ink of apparently the same colour were differentiated when aqueous spots of the ink from the disputed and original entries were transferred direct to a filter paper and examined under ultraviolet rays. The spots from the fraudulent entry fluoresced under the ultraviolet, but not the spots from the original entry. Neither the original nor the fraudulent entry showed any fluorescence when examined directly under ultraviolet light.