Authentication of Postal Pieces by X-Ray Fluorescence with Spatial Resolution

HECTOR JORGE SANCHEZ; M.C. VALENTINUZZI

Arica (Chile)

Congreso; SARX 2006; 2006

At present the authentication of philatelic pieces is a complicated task that usually requires several processes, including the observation and evaluation of experts, the observation with optical microscopes. It is more and more frequent the utilization of more complicated technologies in order to obtain more accurated results. It has been reported the application of infrared analysis and of diffraction techniques. To the authors knowledge, there are few references of the application of XRF techniques for philately and certainly, applications of this technique for philately are not known in Argentina. The utilization of XRF in philately can be very diverse but its basic application consist in the qualitative (quantitative if possible) elemental determination of the components of the different inks used, either on the stamps or on the postage stamps. This allows, after the determination of the constituent elements, to make a comparison with referent inks or the evaluation by using ink catalogues. It can also be used for the identification of elements in zones or specific points that represent some special interest for authentication. One of the most immediate analysis consists on study the inks of the postmarks. The presence or absence of certain elements that are characteristic of the inks (modern inks or of some predetermined period) can determinate the authenticity or falseness of a piece. In this work we present measurements by X ray fluorescence with spatial resolution of the postmark inks of several postal pieces, some of them recognized by experts as authentic ones and others as fake ones. Through the qualitative analysis different comparisons are shown in order to evaluate the possibilities of this technique for the detection of falsifications. The samples analyzed in this work consist of sheets or pieces of sheets (generally parts of letters) containing one or several stamps and/or one or several postage stamps (or postmarks) and usually some kind of handwriting. According to the philatelic experts, all the samples are argentine postal pieces dating from the second half of the IXX century. Samples considered as authentic present important peaks of K, Ca, Fe, Cu and Zn and lower peaks of S, Cl, Ti, V, Cr, Mn and Ni. In the samples considered as fakes some elements are missing (S, Cl, Mn). In other cases the elements are also present in the authentic samples but their intensity is substantially lower (K, Ca, Cu). The results obtained in this work indicate that XRF with spatial resolution is a suitable technique for the authentication of postal pieces through the identification of the elements that constitute the used inks. XRF represents an excellent complement of other techniques and a significative help to the evaluation performed by experts. The systematic implementation of this technique in philately could be enriched by the creation of data bases of compounds and constituents of inks, classified by period, color, use, etc.