Ink The three main groups of modern inks are carbon ink, fountain pen ink, and ballpoint pen ink. Ballpoint pen inks and fountain pen inks both have qualities that gel pen inks share. They are commonly utilised because of how well they write. There are dozens of distinct formulations utilised to create the gel pen inks that are employed in various writing instruments and printing processes. Currently, synthetic organic and inorganic dyes, surfactants, resins, and other ingredients are included in formulations. Acidic dyes and alkaline dyes like sulfonates, chlorosulfonates, or sulfonamides are found in dyes, which make up the majority of ink (1). Additionally, these inks’ durability is improved by additions such very fine pigment dispersions of carbon and Cu-phthalocyanine. The majority of ink formulas are proprietary.
The appearance of inks is merely one indicator of their composition. Although two inks may appear identical to the naked eye, additional tests may be able to identify them. Non-destructive tests are used whenever possible. Inks, for example, can be investigated using infrared or ultraviolet reflectance at various wavelengths, or using visible light but studying ink emissions in the infrared region of the spectrum (infra red luminescence). Ink analysis can also be employed with a VSC 2000HR instrument to do non-destructive specialised illumination studies. Other more intricate chemical tests may be used to differentiate inks, but they are likely to be damaging to some extent. UV-Visible spectroscopy, infrared spectroscopy, chromatography, neutron activation analysis, and visual spectral comparator are all methods for analysing ink.
The instruments and techniques listed below helps in the investigation of ink.
Read Also: Handwriting Examination
Non Destructive Methods
The integrity of a sample with evidential value is critical in forensic examination. As a result, non-destructive approaches are always chosen over destructive ones in order to preserve the integrity of documents.
Prior to the chemical and instrumental analyses, the ink is subjected to a preliminary examination. This includes inspecting ink with microscopes and optical sources without removing the inked section from the document.
The stereomicroscope is used to identify a class of writing instrument by determining the type of ink, its colour, or additional marks made by a sharp tip, blunt tip, or damaged writing tip. This includes determining the ink’s composition. Various light sources, such as UV and IR radiations, are utilized in optical testing because different inks reflect differently with these light radiations.
Video Spectral Analysis of Ink
This gadget is capable of viewing and recording the response of documents/inks to various wavelengths of light. This is useful for inspecting and comparing inks, inspecting security features in papers such as passports and driving licences, inspecting altered or deleted entries, and inspecting entries that have faded or been washed away.
The following lighting and techniques can be combined:
• Visible lighting
• Infrared lighting
• Luminescence infrared
• Ultraviolet light
• Transmitted light
• Coaxial lighting
• Oblique lighting
Techniques that use chemical analysis of the ink on the document come under the category of destructive techniques since the sample is destroyed when a section of the page that contains ink is cut out for examination.
Chromatography is a technique for separating mixtures into the constituent compounds in order to analyse them. It can be used to separate substances like lipstick, ink, blood, and gasoline. In ink chromatography, the colourful pigments that give pens their colour are separated. The ink is actually a blend of various coloured pigments, despite the fact that a pen only writes in one colour.
Capillary electrophoresis has gained popularity due to its advantages of only requiring a small sample, minimising the destruction of the document, and its demonstrated ability to distinguish between various ink types and colours.
The analysis of inks extracted from paper has been done using the technique known as micellar electrophoretic capillary chromatography (MECC). Differences across inks from the same manufacturer can also be detected due to its great resolving power in comparison to inks comprising numerous chemically related ingredients. This makes it appropriate for determining the provenance of documents using the chemical components of inks.
Fourier Transform Infrared spectroscopy (FTIR)
An effective analytical method for determining the chemical “fingerprint” of test samples is Fourier-transform infrared (FT-IR) spectroscopy. Combining attenuated total reflectance accessories with modern design makes handling samples quick and easy while still producing accurate findings. It is particularly desirable to have the evidence or samples preserved in the case of document analysis and many other applications by adopting a nondestructive technology like FT-IR–attenuated total reflectance (ATR).
Fourier Transform Infrared spectroscopy (FTIR) aids in the analysis of ink by utilising IR radiation from the Electromagnetic spectrum.
When these radiations strike a page containing ink, they shake the electrons, releasing energy.
The peaks produced from the graphs of radiated energy aid in determining the functional group of the ink.
Gas Chromatography-Mass Spectrometry (GS-MS)
One of the best methods for analysing ink is to utilise a mass spectrometer in conjunction with gas chromatography to first separate the components, then identify them using the mass/charge ratio.
The use of non-destructive techniques is favoured when examining contested documents unless and until it is absolutely required to do so in order to draw a conclusive decision.