Optical Brightener
Definition
Stilbene-based fluorescent whitening agent added to paper from the early 1950s onwards; under 365 nm UV the paper glows bluish white. A clear absence narrows the paper to pre-1950 manufacture.
- Chemical class
- Stilbene-based fluorescent whitening agent
- Introduced in paper
- Early 1950s onward
- Detection method
- 365 nm UV illumination
- Visible effect
- Bluish-white fluorescence
- Forensic use
- Dating paper as pre- or post-1950s
Common questions
How reliable is the absence of optical brighteners for dating a document?+
Absence is a useful negative indicator, since the additive did not exist in commercial papermaking before the early 1950s, so a genuine absence across the sheet supports an earlier manufacture date. It is not conclusive alone because niche or archival papers may have been produced without brighteners even later.
Can optical brightener fluorescence be faked or removed to mislead an examiner?+
The fluorescence is a bulk property of the paper fibres, not a surface coating, so it cannot be selectively bleached from one area without visibly altering the sheet. Document examiners look for uneven fluorescence across a page as a sign of paper substitution or added sheets.
Related terms
- Aginsky Method
- Solvent-extraction ink-age dating (Valery Aginsky, 1996). Compares fast and slow solvent extractions of phenoxyethanol to derive an aging parameter for ink under...
- ASTM E2789-11
- ASTM standard guide for forensic examination of inks (ink-age dating context). Pairs with ASTM E1422 for paper examination by FTIR.
- Ballpoint Ink
- An oil-based, high-viscosity ink using a resin binder (alkyd or polyamide) in a high-boiling solvent (phenoxyethanol or benzyl alcohol), with triphenylmethane dyes...
- Brunelle R-Ratio Method
- Dye-degradation method (Richard Brunelle and Kenneth Pro, 1972, later refined). Tracks the ratio of extracted and unextracted dye over time to estimate...
- Dye-Based Ink
- Soluble colourant dissolved in solvent. Modern fountain-pen and dye-based ballpoint inks belong here. TLC separates the dye mixture into resolvable spots.
- Gel Pen Ink
- Water-based gel vehicle with pigment particles (often copper phthalocyanine, iron oxide). Behaves like a pigment ink on TLC but more porous on...
- Iron-Gall Ink
- A historical ink formulation of ferrous sulphate, tannic acid (from oak galls), and gum arabic. The ferrous-tannate complex oxidises to brown ferric-tannate...
- LDI-MS / MALDI-TOF
- Laser-desorption mass spectrometry. Reads dye molecular ions directly from the ink stroke with minimal sampling, increasingly used for ink-library searching.
- Phenoxyethanol Decay
- Loss of phenoxyethanol solvent from a ballpoint stroke over weeks to months, measurable by GC-MS or GC-FID. The basis of the Aginsky...
- Pigment Ink
- Insoluble colourant (carbon black, titanium dioxide, organic pigments) suspended in a binder. Pigment particles do not migrate on TLC, so Raman, FTIR...
- Raman Spectroscopy
- A non-destructive laser-based technique sensitive to molecular vibration modes in pigments; complements FTIR by characterising pigment molecular structure rather than bulk ink...
- TLC and HPTLC
- Thin-layer and high-performance thin-layer chromatography. Silica gel plates eluted with ethyl acetate / ethanol / water or methanol / ethanol mixes; Rf...