Chemical Erasure
Definition
Destruction of an ink's chromophore by oxidising or reducing agents (bleach, permanganate, borohydride) without physically removing paper fibres, leaving altered UV fluorescence and residual IR absorption as indicators.
- Agents
- Bleach, permanganate, borohydride
- Mechanism
- Oxidation or reduction of chromophore
- Fibres
- Left physically intact, unlike mechanical erasure
- Detection
- Altered UV fluorescence, residual IR absorption
Common questions
How does chemical erasure differ from mechanical erasure in what it leaves behind?+
Mechanical erasure abrades or removes paper fibres and leaves surface roughening visible under raking light, while chemical erasure destroys the ink's colour-producing structure chemically and leaves the paper surface undisturbed, so the two require different detection techniques.
Why can chemical erasure still be detected even after the ink colour is gone?+
The chemical reaction rarely destroys every trace of the original compound, so infrared absorption from residual ink components and a shift in the paper's UV fluorescence pattern at the treated area often persist even when the entry is no longer visible.
Related terms
- Chromophore
- The molecular subunit responsible for a dye's colour, typically a conjugated double-bond system; chemical erasure destroys the chromophore while leaving the decolourised...
- Interlineation
- Text inserted between existing lines of a document after its original execution; may be detected by ink composition differences, spatial anomalies in...
- Mechanical Erasure
- Physical removal of ink by abrasion (eraser) or shearing (blade), leaving disrupted paper fibres, altered surface texture, and residual ink in fibre...
- Nine-Point Opinion Scale
- The standard framework used by the ASQDE and most international document-examination organisations for expressing conclusions, ranging from identification through elimination with intermediate...
- Obliteration
- Covering of existing writing with an opaque layer (ink, correction fluid, or correction tape) so that the underlying text is invisible in...
- Page Substitution
- Replacement of one or more pages in a multi-page document with forgeries, detectable through paper batch inconsistencies (UV fluorescence, watermark), printing differences,...
- Sizing
- Chemicals applied to paper during manufacture to control ink absorption and surface hardness; mechanical erasure removes sizing from the affected area, allowing...
- SWGDOC
- The Scientific Working Group for Forensic Document Examination (US), which publishes standards for typewriter examination, handwriting comparison, ink analysis, and related forensic...
- Titanium Dioxide (TiO2)
- The white pigment in most correction fluids worldwide; opaque in visible light but largely transparent above ~800 nm near-IR, making IR transmission...