Ink Chromatography (2D) — Forensic Document Ink Comparison

Questioned-document examiners rarely rely on eyesight alone to tell two "black" or "blue" pens apart. Thin-layer chromatography separates each ink into its individual dye components by how strongly they partition between a moving solvent and a stationary silica plate, producing a reproducible fingerprint — the retardation factor, Rf — for every dye. This 2D simulator develops two ink samples side by side on a schematic TLC plate: the solvent front climbs following the Lucas–Washburn √t law (tracked live in its own rise-curve panel) while each dye band separates out at its own Rf and spreads by diffusion. A dedicated bar-chart panel lines up every Rf value from both lanes so a mismatch is visible at a glance. Choose which ink runs in each lane, tune solvent polarity and plate temperature, and watch the live readout and match/mismatch verdict reveal whether a signature was written in the same ink as the surrounding document — or added later with a different pen.