Mechanical Erasure
Definition
Physical removal of ink by abrasion (eraser) or shearing (blade), leaving disrupted paper fibres, altered surface texture, and residual ink in fibre valleys as the primary forensic signatures.
- Methods
- Abrasion (eraser) or shearing (blade)
- Primary signature
- Disrupted paper fibres, altered surface texture
- Secondary signature
- Residual ink trapped in fibre valleys
- Detection tool
- Oblique lighting and microscopy
Common questions
How does an examiner recover text after mechanical erasure?+
Residual ink lodged in the lower fibre valleys often survives surface removal, so techniques such as oblique lighting, infrared imaging, or in some cases chemical development of the remaining pigment can reveal enough of the original strokes to reconstruct wording.
What distinguishes mechanical erasure from chemical erasure under examination?+
Mechanical erasure physically disturbs and thins the paper fibres, producing a visibly roughened or glossy patch, while chemical erasure dissolves the ink without necessarily disrupting fibre structure, so fibre-level microscopy is the key differentiator between the two.
Related terms
- Chemical Erasure
- Destruction of an ink's chromophore by oxidising or reducing agents (bleach, permanganate, borohydride) without physically removing paper fibres, leaving altered UV fluorescence...
- 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...
- 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...