Dyes, Inks, and Paper

Inks consist of a solvent, sometimes called a vehicle, colorants (dyes or pigments), and additives to control flow, thickness, and appearance. Ink was first developed thousands of years ago in China, and early inks were based on carbon black suspended in glue. This is still in existence, now 

TLC is destructive of some of the material under test, but it has the advantage of being quick and inexpensive. Pyridine is recommended as a solvent for glycol-based ballpoint inks, and ethanol/water for non-ballpoint inks. Since 1968, the US treasury has been compiling a library of commercially used inks, and in the 1990s, there was an attempt to persuade manufacturers to tag inks by year of manufacture, but this would need to be a worldwide effort to produce a seriously useful database. 

Dating of inks is difficult and frequently not very reliable. GCMS has been used to identify solvents and volatiles in gel pen ink up to 6 months old, and there are some specialized mass spectrometry studies on particular materials—for example, gentian violet, 26.34, slowly loses methyl groups over time. The only truly reliable determination is to demonstrate that an ink only became commercially available after the date on which the document is purported to be written. 

---