Inks, Papers and Age of Documents

Every ink, whatever the century, breaks into four chemical roles. The vehicle (solvent or oil) carries the rest to the page and sets viscosity, drying speed and stroke feel. The colourant is either a soluble dye or an insoluble pigment. The additives include resins for film formation, surfactants for wetting, biocides, optical brighteners and lubricants. Driers (cobalt, manganese soaps in older inks) accelerate oxidation. Knowing which role a chemical plays is half the work in interpreting a TLC plate or a Raman spectrum.

Six ink families dominate questioned-document casework. Iron-gall ink is the historical workhorse, used from the fifth century into the early twentieth, made of ferrous sulfate, tannic and gallic acids from oak galls, gum arabic binder and water. It starts blue-black and turns brown to rust as iron oxidises; the sulfuric acid byproduct corrodes paper, which is why many Mughal and colonial-era manuscripts in the National Archives of India show characteristic ink burn-through. Dye-based fountain-pen inks (Parker Quink, Bril, Camlin) use water- or glycol-soluble dyes (triphenylmethane, azo, xanthene) and behave well on TLC. Ballpoint inks dominate from the 1950s and use a viscous oily vehicle, typically phenoxyethanol, benzyl alcohol, ethylene glycol or octanol, with dyes (Victoria Blue, Crystal Violet, Methyl Violet, Rhodamine B) and resins (ketone, formaldehyde, alkyd). Gel pen inks (Pilot G2, Reynolds Trimax) suspend pigment particles in a water-gel vehicle and combine the look of a fountain pen with the convenience of a ballpoint. Pigment inks (carbon black India ink, Sumi, modern photo-printer inks) suspend insoluble particles. UV-fluorescent security inks add stilbene, coumarin or europium-chelate fluorophores; Indian currency, passports and stamp paper carry layered fluorescent and infrared-absorbing inks specified by the Reserve Bank of India and printed at the Bharatiya Reserve Bank Note Mudran (BRBNMPL) presses at Mysore and Salboni.

The comparison workflow runs non-destructive first, destructive last. A trained examiner starts with the cheapest, lowest-impact tools and only sacrifices sample when the question stays open.

Visual and microscopic examination. Stereomicroscope at 10x to 40x reads stroke morphology, line quality, ink-on-ink crossings and pen-pressure indicators. Video Spectral Comparator (VSC 8000, foster + freeman) gives reflected, transmitted and side lighting, plus filtered UV (254 nm, 365 nm) and IR (up to about 1000 nm) imaging. Two inks that look identical under tungsten can split under 645 nm IR-reflected light if one absorbs and the other does not. GEQD Shimla, GEQD Hyderabad and GEQD Kolkata each operate VSC-grade instruments as standard.

Thin-layer chromatography (TLC). The oldest workhorse for dye-based inks. A tiny ink plug is extracted with pyridine, methanol or ethanol-water (1:1), spotted on a silica gel plate, and eluted. The classic eluent for ballpoint dyes is ethyl acetate : ethanol : water (70:35:30 by volume), sometimes with n-butanol. Modern labs prefer HPTLC on pre-coated silica plates with densitometric scanning, which gives quantitative band areas and Rf reproducibility good enough for ink-library searching. The US Secret Service International Ink Library holds reference TLC patterns for roughly 10,000 inks and supplies the de facto global comparison standard.

Raman spectroscopy. Non-destructive, in-situ on the page. 785 nm excitation is the workhorse for inks because it suppresses paper-cellulose fluorescence that swamps 532 nm spectra; 1064 nm FT-Raman suppresses fluorescence further but needs more sample. Raman identifies dyes (Crystal Violet at 1175 and 1620 cm-1, Methyl Violet, copper phthalocyanine pigment in blue gel inks) and discriminates ballpoints that look identical on TLC.

FTIR microspectroscopy. Diamond-cell or ATR FTIR of a microsampled ink stroke reads the resin and vehicle bands (C-H stretch 2900 cm-1, C=O 1720 cm-1, aromatic ring 1600 cm-1). Pairs naturally with

Paper examination answers three questions: what is the paper made of, who made it, and when. Fibre source is read by macerating a fibre fragment in water, staining with Herzberg reagent (zinc chloroiodide; chemical pulp stains blue-violet, mechanical groundwood stains yellow), and reading under a polarising microscope. Wood-pulp paper (softwood pine, spruce or hardwood eucalyptus) dominates modern office paper; rag paper (cotton or linen) is reserved for currency, stamp paper, ledgers and archival manuscripts. Indian currency notes use a high-cotton rag pulp blended with a small wood-pulp fraction, produced at SPM Hoshangabad (Security Paper Mill, Madhya Pradesh) and BNPM Mysore (Bank Note Paper Mill India, a joint venture between SPMCIL and BRBNMPL).

Watermarks are made during paper formation by a raised pattern on a dandy roll (cylinder-mould or modern Fourdrinier process) that thins the wet fibre mat. Held against light, the pattern shows lighter than the surrounding sheet. Indian Rs. 100, Rs. 200, Rs. 500 and Rs. 2000 (where still circulating) carry Mahatma Gandhi watermark, multitone shade pattern and electrotype denomination. BIS specifications IS 1848 and IS 7257 cover security and currency-grade paper; the watermark catalogue at GEQD Shimla supports counterfeit-document casework.

Optical brighteners (OBA) are stilbene-based fluorescent whitening agents added to paper from the early 1950s onwards. Under 365 nm UV the paper glows bluish white. Clear absence of OBA fluorescence narrows the paper to pre-1950 manufacture, a single-question dating tool that turns up in many backdated-will cases. Different mills use different OBA blends; the fluorescence emission profile under VSC sometimes distinguishes paper batches.

Fillers are inorganic particles loaded into the sheet to improve opacity, brightness and printability. Calcium carbonate (CaCO3), titanium dioxide (TiO2),

Document dating splits cleanly into ink-age dating (how long has this ink been on the page) and paper-age dating (how old is the sheet of paper itself). NTA tests both, and the chemistry is different.

Ink-age dating: the solvent-decay route. A fresh ballpoint stroke loses phenoxyethanol, benzyl alcohol and other vehicle solvents over weeks to months as they evaporate and migrate into paper. Valery Aginsky (1996) built the dominant method around this. A small ink plug is plug-extracted with a strong solvent for a short time and again with a weak solvent for a longer time; the ratio of the two extractions gives an aging parameter R% that drops as the ink dries and the vehicle binds into the paper. The method works best on ballpoint inks under about two years old; beyond two years the solvent has effectively left the page and the parameter plateaus. GC-MS or GC-FID quantifies phenoxyethanol; some labs use thermal-desorption GC-MS for ultra-low sampling.

Ink-age dating: the dye-degradation route. Brunelle and Pro (1972) and Brunelle (1995) developed the R-ratio method, comparing the ratio of extracted dye in a weak solvent to extracted dye in a strong solvent. Dyes degrade and bind to paper over time; the R-ratio shifts. Best applied as a relative comparison between two strokes on the same document.

ASTM E2789-11 ("Standard Guide for Examination of Inked Crossings") and the broader ASTM ink-age dating literature codify the procedure expectations. The fundamental rules: only inks of the same formulation can be cross-compared; the reference must come from the same document and paper; and the conclusion is expressed as a range ("less than 6 months", "between 6 months and 2 years", "more than 2 years"), not a single date. Indian appellate courts have accepted ink-age opinions from GEQD Hyderabad and CFSL Hyderabad in property-disputes and will-contest cases, though always under the

Document examination in India lives in two parallel networks. The Government Examiner of Questioned Documents (GEQD) offices at Shimla, Hyderabad and Kolkata sit under the Directorate of Forensic Science Services and handle Central Government and railway casework. The CFSL network (Chandigarh, Hyderabad, Kolkata, Pune, Bhopal, Guwahati, New Delhi-CBI) handles state-police, CBI and inter-state cases. CFSL Hyderabad runs a dedicated ink-analysis unit with VSC, HPTLC, FTIR and Raman, and is the lead lab for ink-age dating casework in southern India. NFSU Gandhinagar runs teaching and casework programmes in questioned documents and supplies LDI-MS access for the network.

The paper side anchors at SPM Hoshangabad (Security Paper Mill, Madhya Pradesh, established 1968, supplies security paper to Indian Government Printing Presses) and BNPM Mysore (Bank Note Paper Mill India, JV between SPMCIL and BRBNMPL, supplies currency-grade rag paper). BIS standards IS 1848 (security paper) and IS 7257 (printing paper) set the specification frame.

The statutory frame is the Bharatiya Sakshya Adhiniyam 2023 (BSA). Section 39 governs expert opinion on questioned-document chemistry. Section 60 preserves the right to call for and compare handwriting and signatures. The BNSS 2023 Section 348 (formerly Section 311A CrPC, formerly Section 73 IEA 1872) allows a magistrate to direct an accused to produce specimen writing, signature or other comparison samples. For electronic records (scanned documents, PDF wills, e-stamp paper), BSA 2023 Sections 61 and 63 carry the electronic-record certificate requirement. The combined frame for forensic evidence under the BSA 2023