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.Chemical and physical analysis of inks on questioned documents provides valuable information regarding their authenticity.Comparison of these chemical and physical properties of two or more inks can determine: (1) if the inks were made by the same manufacturer; (2) in some cases, whether the inks are products of the same production batch; and (3) the first production date of the specific ink formulation involved.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.
Ballpoint inks consist of synthetic dyes (sometimes carbon or graphite is also added for permanence) in various glycol solvents or benzyl alcohol.
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.
It is made into a liquid for writing by grinding the cake and suspending the particles in a water-glue medium. Liquid carbon inks are also commercially available.
In the liquid carbon inks shellac and borax are used in place of animal glue and a wetting agent is added to aid in the mixing of the shellac and carbon.