Fourier transform infrared spectroscopy applied to ink characterization of one-penny postage stamps printed 1841–1880 Original Research Article

Fourier transform infrared spectroscopy (FTIR) was applied to the characterization of red inks used to print one-penny stamps in Britain during the period 1841–1880. Micro- and macro-accessories were compared in both transmission and reflection mode. The best spectra were obtained using a microscope with a diamond cell coupled to an infrared spectrometer. In this case, the extraction of a single paper fibre was enough to obtain a good spectrum. Calcium carbonate, calcium sulfate, lead chromate, cyano compounds, cellulose, and oil were identified. When bigger surfaces need to be analyzed, diffuse reflection or variable specular reflectance accessories can be used. Nevertheless, only cyano compounds and calcium carbonate can be characterized. Results are in agreement with those obtained using scanning electron microscopy. The chronological order of the 71 stamps studied showed that the chemical composition of the red ink changed during the period studied.