Spectral characterization of Argentine postage stamps using complementary in situ and non-invasive techniques

Abstract

This work studies the different materials used in the production of Argentine postage stamps from 1888 to 2016 and explains how the use of these materials has changed over time, thus contributing to knowledge of the national philatelic heritage. Analyses of more than 40 Argentine postage stamps were carried out non-invasively in situ without the need for prior preparation, using portable X-ray fluorescence spectroscopy (p-XRF) and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). Paper, ink, coatings, and adhesives were analysed and the period of use of each material was established. Some notable results include the continuous use of Prussian blue until its replacement by an organic copper phthalocyanine pigment. In addition, it was possible to establish the substitution date of gum arabic as an adhesive by PVA. In general, the variation of the materials used was accompanied by changes in printing techniques. This is the first time that information on the materiality of these historical-artistic objects is published, contributing to the knowledge and conservation of the philatelic heritage of the Argentine Republic.