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Relative age comparison tests performed on inks of the same formula and written on the same type of paper with the same storage conditions (performed by measuring changing solubility properties of inks) can estimate how long inks have been written on paper.
This is done by: (1) comparing the rates and extents of extraction of questioned and known dated inks in organic solvents by thin-layer chromatography (TLC) densitometry; (2) comparing changes in dye concentrations by TLC and TLC densitometry; and (3) comparing the volatile ink components by gas chro-matography-mass spectrometry (GC-MS).
Red, green, yellow and other colored chelated dyes are now used for various colored ballpoint inks.
Ballpoint inks consist of synthetic dyes (sometimes carbon or graphite is also added for permanence) in various glycol solvents or benzyl alcohol.There are two types of fountain pen inks: (1) iron-gallotannate type and (2) aqueous solutions of synthetic dyes.Modern inks of type (2) contain synthetic blue dyes to provide an immediate blue color to the ink which gradually turns black after oxidation on paper.These ingredients consist of fatty acids, resins, surface active agents, corrosion control ingredients and viscosity adjustors.The fatty acids (oleic is the most common) act as lubricants to the ball of the pen and they also help the starting characteristics of the ball point.
These pens contain a pressurized feed system instead of gravity flow.