Ink Analysis


Figure 1 



The term "ink analysis" usually refers to chemical tests which are applied to small samples of ink removed from a document. The traditional method for analyzing writing inks is Thin Layer Chromatography (TLC). It  involves removing several "plugs" of ink and paper from the document, placing them in a small vial where a solvent is added to dissolve the ink. Once extracted, the ink is spotted on a high performance plate.

The plate is then placed in a developing tank and a solvent system is added to the chamber. The specific solvent system is chosen based on the type of ink being tested.  The solvent soon migrates up the plate carrying the ink with it. Based on the physical and chemical components which make up the ink, distinct bands form on the chromatographic plate. 

The band patterns corresponding to ink removed from three different areas of a document (Figure 1) show that samples #1 and #3 have a similar formulation while ink #2 contains different components than the other two. This supports the Plaintiff's claim that the document was altered sometime after he signed it.

In addition to being a powerful tool for distinguishing writing inks, TLC is also used to isolate dating tags that have been added to inks by some manufacturers.