Dating of Seals Produced with Stamp‐Pad Ink Using Gas Chromatography Method

Seals are often placed on important documents, and determining the date when a seal was affixed can be important to assess the authenticity of a document. In this study, thirty‐seven different brands of stamp‐pad inks and three different types of paper were used to make diachronic samples of the seals. The volatile components of stamp‐pad ink were determined, and the stamp‐pad ink was classified by gas chromatography with a flame ionization detector. Calibration curves were created to show the relationship between the content of volatile stamp‐pad ink components and the age of stamp‐pad ink entries stored under natural aging, UV‐induced aging, and heating aging conditions. The experimental results showed that GC was useful in the analysis of stamp‐pad ink and applicable for determining the relative age of stamp‐pad ink entries in some cases where the seal was placed on the document within 3 months.