Over the past 20 years, no other field of forensic science has had greater impact on the detection of fraudulent documents than the scientific examination of writing inks. This paper traces the development of ink dating techniques from the 1930s to 1990. Techniques used during this period are described and, when possible, illustrated. The emphasis is on ink dating techniques used today, with discussion of the value and limitations of these procedures.

A new single-solvent extraction technique was developed to estimate the relative age of ballpoint inks. The procedure involves extracting the inks with weak solvents, spotting the ink extract onto a thin-layer chromatographic plate and measuring the amount of ink extracted densitometrically. By comparing the amount of questioned ink extracted with the amount extracted by known dated inks, it is possible to estimate the date the questioned ink was written. Success in using this technique depends on finding suitable weak solvents for extracting the ink. It also depends on the ability of the analyst to remove nearly equal amounts of ink from the document for each ink sample tested. This paper describes the results of several experiments for determining the relative age of ballpoint inks using a single extraction technique. Reproducibility measurements, experimental variations, and the limitations of the technique are also reported. Suggestions for further work are proposed.

A systematic approach to identification of writing inks is presented. This approach uses a multiple technique method for analysis of the inks to develop a large number of identifiable points for comparison. Well established methods are used for the analysis of inks, such as thin layer chromatography, spectrophotometry, and gas-liquid chromatography, in addition to traditional methods for comparison which use ultraviolet and infrared light. The inks are identified by comparing the results of the questioned inks with results obtained from a complete library of writing inks maintained by this laboratory. By using the described approach, most inks can be identified with a high degree of certainty.

Advances in ways to date inks have been publicized over the past 17 years. As a result, Government agencies and the private sector now rely heavily on these techniques in criminal and civil litigations. As new procedures have become known, more forensic scientists are asked to perform ink dating examinations. While the capabilities of these techniques are generally known, their limitations are not. This paper evaluates the current approaches used for dating writing inks and takes a critical look at conclusions that can be made on the basis of the different laboratory techniques.

Brunelle et al. (Journal of Forensic Sciences. Nov. 1987) recently reported a single-solvent extraction technique for determining the relative age of ballpoint ink entries on questioned documents. This technique was mass dependent, which means equal amounts of ink had to be removed from the document for all samples compared. This paper describes a modification of the previous procedure that makes the age determination independent of the amount of ink sampled for testing. The modified procedure involves extracting the inks with solvents, spotting the ink extract onto a thin-layer chromatographic plate, and then separating the dye components in a solvent system of ethyl acetate: alcohol: water (70:35:30 parts, respectively). The relative concentrations of the dye components are measured using a densitometer. The calculated ratios of the relative concentrations are independent of the amount of ink taken for analysis. Aging curves were prepared for four different ballpoint inks and two non-ballpoint inks. The effect of different papers on ink aging was determined, and the mass independence theory was verified. The feasibility for determining the relative age of non-ballpoint inks was also established.