Ink dating techniques
The dyes in ballpoint inks can consist of up to 50% of the total formulation.Several other ingredients are usually added to the ink to impart specific characteristics.In 1946, several million Reynolds ballpoint pens reached the market in the United States.Ballpoint inks consist of synthetic dyes (sometimes carbon or graphite is also added for permanence) in various glycol solvents or benzyl alcohol.Ballpoint inks made before about 1950 used oil-based solvents such as mineral oil, linseed oil, reci-noleic acid, methyl and ethyl esters of recinoleic acid, glycerin monoricinoleate, coconut fatty acids, sorbi-tal derivatives, and plasticizers such as tricresylpho-sphate.Modern ballpoint inks (post-1950) are referred to as glycol-based inks, because of the common use of ethylene glycol or glycol derivatives as a solvent for the dyes.The composition is basically the same, but this ink does not become fluid until disturbed by the rotation of the ball point in the socket.
The physical characteristics of these inks are quite different from the standard glycol based ballpoint inks.
Red, green, yellow and other colored chelated dyes are now used for various colored ballpoint inks.
Pressurized ballpoint inks were developed about 1968.
This article describes state of the art procedures for the chemical and physical comparison, identification and dating of inks on questioned documents.
Knowledge of the composition of inks is necessary to understand the reasons for the various methods used to analyze inks.