Changes in composition of ballpoint pen inks on aging in darkness.

A method for comparison of the relative age of ink entries written by the same ballpoint pen on documents stored in darkness is presented. Inks were extracted from the document and analyzed by HPLC (high performance liquid chromatography). On aging, changes in the chemical composition of the inks were noted. These changes were similar to those observed when inks were exposed to light or heat. The aging was followed by using ternary diagrams constructed for dyes generally present in blue-colored inks--Crystal Violet, Methyl Violet, and Tetramethyl Para Rosaniline. The procedure is applicable for relative dating of ink entries in diaries, notebooks, etc., where often several ink entries are written by the same ink. However, a prolonged exposure of the document to daylight and/or artificial light (light from fluorescent tubes) as well as to extensive heat will render the whole procedure inapplicable. An example of the use of the proposed method in casework is given.