FTIR spectra of all postage stamps in a country's history
- Published: Jul 9, 2013
- Author: Steve Down
- Channels: Chemometrics & Informatics / Raman / MRI Spectroscopy / Infrared Spectroscopy / X-ray Spectrometry / Proteomics / NMR Knowledge Base / Base Peak / UV/Vis Spectroscopy
The ATR-FTIR spectra of examples of all of the postage stamps produced in Italy since 1862 have been collected. That might seem a strange operation to carry out but the research team had two main objectives in mind: mapping the changes in production techniques, glues and coatings over the years, and establishing a database which can be used to detect counterfeit stamps.
Ludovico Valli and co-researchers from the University of Salento in Lecce examined pristine and cancelled stamps produced throughout Italian history and the spectra were able to characterise the type of paper, filler, coatings, glues and the gum on the reverse side by this non-destructive technique which left the samples intact.
The different periods in stamp production were distinguished, as described in Analytical Chemistry. The original use of cellulose fibres seized with gelatin glue, the introduction and subsequent elimination of kaolin, and the transition from protein glue to starch glue to poly(vinyl alcohol) on the reverse side were all followed, providing a timeline of the main innovations in Italian stamp production.
Apart from the historical importance, the databse can be used to detect fake postage stamps. In one case, a suspect Gronchi Rosa (Pink Gronchi) was confirmed by the absence of kaolin in the paint. There are many fake examples of this stamp because of its rarity. It was withdrawn one day after issue when it was spotted that the boundaries of Peru were drawn incorrectly.
A second stamp, issued in 1865, was shown to have been regummed. The presence of poly(vinyl acetate) gave the game away since this polymer was not even synthesised for the first time until the 20th Century. The presence of the original gum on the back of a stamp can raise its price, hence the deception.