Terminus Post Quem
Definition
Latin for 'limit after which'; in document dating, the earliest possible date for a document, established when a material component (paper, ink, OBA) was not available before a known date.
- Meaning
- Latin for limit after which
- Field
- Document and ink dating
- Basis
- Introduction date of a material component
- Type of date
- Earliest possible, not exact
Common questions
What kind of material sets a terminus post quem for a document?+
A component such as a specific paper formulation, an optical brightening agent, or an ink dye that only entered commercial production after a known year fixes that year as the earliest the document could have been made.
Can a terminus post quem be wrong?+
Yes, if the reference date for when a material first became available is itself uncertain or if an unusual, pre-release sample was used, the calculated earliest date can be pushed later or earlier than the true one.
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...
- 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;...
- Watermark
- A pattern formed in paper during manufacture by localised fibre-density variation on the Fourdrinier wire; visible in transmitted light as a lighter...