An Inside Look at X-ray Techniques in Stamp Collecting

A recent study explored how spectroscopy can be applied to stamp collecting, also known as philately. A couple of researchers from the Universidad Nacional de Córdoba in Argentina proposed a new approach that they claim can improve the authentication of postal stamps. This study, which was published in the journal Spectrochimica Acta Part B: Atomic Spectroscopy, investigates the effectiveness of using energy-dispersive inelastic X-ray scattering (EDIXS) to differentiate between types of inks used in cancellation marks (1).

Philately is a hobby that involves people collecting different types of stamps. The appeal of this hobby is that different stamps have historic and monetary value (2). Stamps are also appreciated for their aesthetic value, and many collectors consider them miniature works of art (2). However, because of these reasons, forgery is unfortunately a concern. In the past, experts have generally used X-ray fluorescence (XRF) spectroscopy with principal component analysis (PCA) to analyze stamps.

This method, although not terrible by any means, does not always provide precise classifications. XRF primarily captures information related to the combined composition of ink and paper, but because paper composition can vary significantly across decades, this limits how useful the technique could be (1).

The researchers demonstrated in their study that EDIXS provides a more refined analysis by probing atomic environments and oxidation states, which are crucial for differentiating inks themselves rather than the paper substrate (1). As part of the experimental procedure, the researchers analyzed nine Argentine stamps spanning nearly a century, focusing on the iron Kα-RIXS peak region (1). Their PCA of the EDIXS data revealed distinct clusters corresponding to different ink chemistries. Although some overlap occurred, several inks were clearly distinguished, underscoring EDIXS’s potential for ink discrimination (1).

The findings of the study reveal that EDIXS can isolate the chemical-state information, which is critical for confirming stamp authenticity. Moreover, the researchers utilized synchrotron radiation, which is a highly advanced form of X-ray technology (1). Unlike traditional sources, synchrotron radiation generates finely tuned, intense beams that allow for detailed, non-destructive analysis (1). This is particularly valuable for fragile cultural heritage artifacts like stamps, where preservation of the original condition is important to collectors.

The researchers conclude their study by explaining that while EDIXS was effective, there were some limitations with their study. They explained in their article that the overlapping regions in the PCA analysis indicate the need for expanded measurements and direct comparisons between samples (1). Nevertheless, this study represents the first demonstration of EDIXS in characterizing postal cancellation inks, marking an important step toward more reliable stamp authentication (1).

References

1. Sanchez, H. J.; Leani, J. J. Discrimination of Postal Stamps via Energy-dispersive Inelastic X-ray Scattering (EDIXS): Differentiating Inks Beyond Elemental Composition. Spectrochimica Acta Part B: At. Spectrosc. 2025, 233, 107289. DOI: 10.1016/j.sab.2025.107289
2. Driscoll, S. Stamp Collecting. EBSCO. Available at: https://www.ebsco.com/research-starters/history/stamp-collecting (accessed 2025-08-26).