Spectroscopically generated curves are plotted as the ratio of reactants to products, versus time.
The spectral characteristics of the ink are determined in units of percent reflectance of the active compounds in the ink so that the age of the ink can be computed by reference to known reaction rates.
This is because the concepts of absolute and relative aging are not clearly understood.
By Nato Locktongbam Central Forensic Science Laboratory, Directorate of Forensic Science Services, Ministry of Home Affairs, Government of India, Kolkata Dr. In order to address these challenges, an attempt was made to study the rate of diffusion of inks at different time intervals using hyperspectral imaging. One of the challenges faced by the forensic document examiner is determining the age of a document/ink in order to ascertain whether entries or writings – such as those in logbooks, registers, OMR sheets, deeds, cheques, drafts, and other important documents – were executed in the same period or in different periods of time. Many attempts have been made to determine the age of ink in the last 30 years. The aim of this work is to characterize the degradation processes of methyl violet and ethyl violet, two typical ballpoint dyes by using laser desorption/ionization (LDI) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS), and to evaluate the possible application of the method to forensic examination of documents.The mass spectrometric methods were first tested and were found to be adequate for the purpose of this work.