RELATIONSHIPS BETWEEN NATURAL AND ARTIFICIAL AGING OF PURE INK DYE: MODEL STUDY USING CRYSTAL VIOLET

Abstract

Inks in written documents fade over time due to physicochemical changes caused by exposure to environmental factors like oxygen, humidity, light, and heat. This fading is examined in detail with advanced analytical methods. The age of a document can be determined from the amount of ink fading. In this study, a ballpoint pen ink containing Crystal Violet as the major component was prepared and changes to pure crystal violet over time were examined. Ink samples were prepared by printing from a cartridge filled with this crystal violet solution onto paper and exposed to artificial daylight for 33 hours. Changes in the ink composition were analyzed using High Performance Liquid Chromatograpy. Additionally, inks from naturally aged documents were analyzed in the same manner, and the dye ratios were investigated to compare the parameters for dye aging in dark, or only weakly exposed to daylight, rooms. We found that the dye ratio and degradation product peaks on the chromatogram contained useful information related to ink aging rather than the absolute amounts of crystal violet, methyl violet, and tetramethyl pararosaniline. A chromatogram from a real case sample (fraudulent documents that were exposed to high intensity light) that tricked expert witness on ink dating was obtained and presented.