Dye-Decay Dating (LaPorte Method)
Definition
An ink dating method that uses HPLC-PDA to monitor the relative concentrations of specific dye components and their degradation products; the ratio of degradation products to parent dye increases with age, providing an ageing index for ballpoint inks.
- Applies to
- Ballpoint pen inks
- Technique
- HPLC-PDA
- Measured
- Ratio of degradation products to parent dye
- Trend
- Ratio increases with ink age
Common questions
What limits the reliability of the LaPorte dye-decay method for dating a specific document?+
Degradation rate depends on storage conditions such as light exposure, temperature, and humidity, so the method generally works best for relative comparisons or broad age ranges rather than pinpointing an exact writing date without a matched reference sample stored under similar conditions.
How does dye-decay dating differ from solvent-loss ink dating methods?+
Solvent-loss methods track the evaporation of volatile solvents that occurs mainly in the first months after writing, useful for very recent documents, while dye-decay dating tracks chemical degradation of the dye itself, which continues over a longer timescale and suits older documents.
Related terms
- Aging Index (Aginsky)
- The ratio of phenoxyethanol concentration in an unheated (cold) extract to its concentration in a heated extract from the same ink stroke;...
- ASTM E2494
- ASTM International's Standard Guide for Using Ink Examination Methods in Questioned Document Investigations; sets out the recommended tiered analytical approach, uncertainty reporting...
- Machine Direction (MD)
- The direction parallel to paper travel through the papermaking machine; cellulose fibres preferentially align in this direction, making machine-made paper stronger and...
- Optical Brightening Agent (OBA)
- A fluorescent compound added to paper pulp or coatings that absorbs UV-A radiation and re-emits it as visible blue light, making paper...
- Plateau Effect
- The upper age limit of ink solvent-loss methods (approximately 5-7 years in most storage conditions), beyond which phenoxyethanol has been substantially lost...
- Rag Paper
- Paper made from cotton or linen rags, yielding long, low-lignin cellulose fibres; the dominant writing-paper substrate before approximately 1870 and still used...
- Solvent-Loss Method
- An ink dating approach that measures the residual concentration of semi-volatile solvents (particularly phenoxyethanol in ballpoint inks) relative to a non-volatile reference;...
- Terminus Post Quem
- Latin for 'limit after which'; in document dating, the earliest possible date for a document, established when a material component (paper, ink,...
- Watermark
- A pattern formed in paper during manufacture by localised fibre-density variation on the Fourdrinier wire; visible in transmitted light as a lighter...