The potential of artificial aging for modelling of natural aging processes of ballpoint ink

Abstract

Artificial aging has been used to reproduce natural aging processes in an accelerated pace. Questioned documents were exposed to light or high temperature in a well-defined manner in order to simulate an increased age. This may be used to study the aging processes or to date documents by reproducing their aging curve. Ink was studied especially because it is deposited on the paper when a document, such as a contract, is produced. Once on the paper, aging processes start through degradation of dyes, solvents drying and resins polymerisation. Modelling of dye's and solvent's aging was attempted. These processes, however, follow complex pathways, influenced by many factors which can be classified as three major groups: ink composition, paper type and storage conditions. The influence of these factors is such that different aging states can be obtained for an identical point in time. Storage conditions in particular are difficult to simulate, as they are dependent on environmental conditions (e.g. intensity and dose of light, temperature, air flow, humidity) and cannot be controlled in the natural aging of questioned documents. The problem therefore lies more in the variety of different conditions a questioned document might be exposed to during its natural aging, rather than in the simulation of such conditions in the laboratory. Nevertheless, a precise modelling of natural aging curves based on artificial aging curves is obtained when performed on the same paper and ink. A standard model for aging processes of ink on paper is therefore presented that is based on a fit of aging curves to a power law of solvent concentrations as a function of time. A mathematical transformation of artificial aging curves into modelled natural aging curves results in excellent overlap with data from real natural aging processes.

Application of time of flight secondary ion mass spectrometry to the in situ analysis of ballpoint pen inks on paper

“…hyphenated approach [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. MS has the advantage of high sensitivity and the ability to produce highly characteristic spectra that can offer a high level of discrimination.…”

Minimum requirements for application of ink dating methods based on solvent analysis in casework

“…The results thus obtained are then used for calculating a similar aging parameter as the one proposed by Aginsky (D in Table 4) [33] with the difference that the subsequent samples are aged naturally instead of artificially. In fact, artificial aging is faster, but actually still debated largely in the scientific community and it was not yet demonstrated to reproduce adequately the natural aging of ink [42]. In this way, using the V% values of the five samples, each of which is older than the previously analysed, an aging curve for the questioned ink entry is obtained.…”

“…As explained above, ink aging pathways and rates are significantly influenced by a number of factors that may slow down or accelerate the phenomenon [42,61]. These parameters must therefore be extensively studied before a conclusion can be drawn on the absolute age of an ink entry.…”

“…It was based on the changes in the extractability of the ink supposedly caused by the hardening of the resins [10,[21][22][23][24]. The use of this technique in caseworks was reported in the literature [18,25], but it was followed by a vigorous controversy among the scientific community about the limitations of this approach [5,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Several researchers tried reproducing the results obtained in previous studies and reported the methods to be unreliable [28,[34][35][36], while other scientists debated about the necessity for inter-laboratory validation before their use in casework [4,27,[31][32][33]38,41].…”

Fast and Simple Forensic Red Pen Ink Analysis Using Ultra-Performance Liquid Chromatography (Uplc)

“…Therefore, the final composition of inks can be quite complicated. In general, ballpoint pen ink comprises of 50 % solvent, 25 % dyes as well as 25 % resins and other additives [4]. In most cases, ink analysis always focuses on dye components because of their ability to absorb light of different wavelength [5].…”