Plateau Effect
Definition
The upper age limit of ink solvent-loss methods (approximately 5-7 years in most storage conditions), beyond which phenoxyethanol has been substantially lost and the aging index ratio no longer discriminates between older inks; absolute dating is unreliable beyond this plateau.
- Applies to
- Ink solvent-loss aging methods
- Age limit
- Approximately 5 to 7 years under most storage conditions
- Cause
- Substantial loss of phenoxyethanol beyond that age
- Consequence
- Aging index no longer discriminates between older inks
Common questions
Why can't solvent-loss dating simply be extrapolated beyond the plateau age?+
Once the volatile solvent component has largely evaporated, the aging index stabilises near a floor value regardless of how much older the ink actually is, so extrapolating the same curve past that point would give an unreliable or meaningless estimate.
What does the plateau effect mean for dating an old, disputed document?+
It sets a practical upper limit on how precisely ink age can be determined by solvent loss, so for documents suspected to be many years old, examiners rely more on other dating approaches such as dye component analysis rather than solvent loss alone.
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...
- Dye-Decay Dating (LaPorte Method)
- An ink dating method that uses HPLC-PDA to monitor the relative concentrations of specific dye components and their degradation products; the ratio...
- 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...
- 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...