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.
In cases where known dated writings are not available for comparison with questioned inks, accelerated aging (heating the ink to induce aging of the ink) can sometimes be used to estimate the age of ink using any or all of the above described techniques.Iron-based inks can be dated by measuring the migration of iron along the fibers of the paper by Scanning auger microscopy.Benzyl alcohol is also commonly used as the vehicle (solvent) by some ink manufacturers.Chelated dyes (introduced commercially around 1953) are stable to light.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.
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.
When dating tags are detected, it is possible to determine the actual year or years when the ink was manufactured.
Dating tags are unique chemicals that have been added to ball-point inks by some ink companies as a way to determine the year the ink was made.
In 1946, several million Reynolds ballpoint pens reached the market in the United States.