Spectral Database for Postage Stamps by Means of FT-IR Spectroscopy

Abstract

A Fourier transform infrared (FT-IR) spectroscopy study on the entire Italian postage stamps production is presented in this work. Crossing 150 years of issues from the unification of Italy until today, a time line of the major components constituting the stamps has been defined, based on the wide spectral database built on the basis of the numerous analyzed exemplars. Even though it is easy to find reports about stamps' issues history, information arising from these investigations contributes to throw light upon the substances incorporated in the stamps, which could be described as hybrid or composite materials (a sort of undisclosed or hidden story). As a result of the whole spectra acquired in attenuated total reflectance (ATR) mode, changes in paper composition showed the transition from the protein sizing glue to starch sizing; also the employment of kaolin varied through time. First it was used as the extender in the pigment-medium mixture, and finally it constituted the coating on the stamp surface. Also the chemical composition of the adhesive gum on the rear side of stamps has been subjected to modifications, as well as the front side. The earliest back glue was a protein-based adhesive; then it was replaced by gum arabic first and by poly(vinyl acetate) (PVAC) later. FT-IR spectroscopy, supported by the detailed database developed, has been applied, for the first time, in the very useful detection of two counterfeit samples: a fake of the famous Gronchi Rosa, issued in 1961, and a regummed 2 cent red stamp, issued in 1865. The information held in the whole spectral data has been selected and employed in the principal component analysis (PCA) statistical analysis.

Spectral investigations on 1000£ banknotes throughout Italian Republic

“…Because of the non-destructiveness of the employed setup, every single specimen was directly placed onto the ATR plate with no further preparation and an optimal contact between the surface of the sample and the diamond crystal was ensured by means of a piston [8]. For all samples, thirty-two scans were collected with 4 cm À1 resolution in the range between 4000 and 600 cm À1 .…”

“…Cinnabar was found in the composition of the red number printed on one of the stamp analyzed in this study from the 1918 issue. This pigment has been utilized in antiquity as red pigment for ancient manuscripts and also the application of this pigment on Italian stamps was attested until 1863 [8]. The mark with the Medusa was also used on the second 1000 £ in 1962 and it is positioned in a circular frame with equidistant pearls on the bottom front of the banknote.…”

“…The band at 1582 cm À1 can be assigned to the naphthalene structure as for the 986 and 726 cm À1 absorptions [21], while the signal at 1484 cm À1 is the stretch of the À ÀN¼NÀ À group [21]; the strong peak at 1332 cm À1 is related to the presence of an aromatic nitro group and the CÀ ÀN symmetrical stretch is evident at 1115 cm À1 [21]. Bright red b-naphthol pigments were also used on Italian stamps dating from 1923 [8] and in red Hungarian postage stamps with FIUME overprint from 1918 [20]; therefore is not unusual their employment in printing inks from that period.…”

“…The usage of phthalocyanines is known on Italian postage stamps, too, since [ ( F i g . _ 4 ) T D $ F I G ] 1958 [8]. Copper phthalocyanines are widely commercially used as blue and green organic pigments in printing inks [26] and they are the same kind of pigments still in use today in modern postage stamps [8].…”

“…_ 4 ) T D $ F I G ] 1958 [8]. Copper phthalocyanines are widely commercially used as blue and green organic pigments in printing inks [26] and they are the same kind of pigments still in use today in modern postage stamps [8]. The banknote Montessori was issued by the Bank of Italy in 1990, and remained in circulation until the introduction of the euro in 2002.…”