Problems of Forensic Sciences 2006 Vol. 67 (LXVII) 249-254
ANALYSIS OF THE INFLUENCE OF SURFACE, PASSAGE OF TIME AND CONDITIONS OF STORAGE OF DOCUMENTS ON OPTICAL PROPERTIES AND RAMAN SPECTRA OF INKS
Ewa FABIAŃSKA, Marcin KUNICKI
Institute of Forensic Research, Krakow, Poland
Streszczenie
When performing expert analysis of questioned documents, in the first, fundamental stage of differentiation of writing materials, non-destructive methods are used routinely, including, above all, optical methods and Raman spectroscopy, on the basis of which final conclusions are formulated or decisions are made concerning further analyses. It is known that the type of surface and method of storing documents influence the optical properties of inks. The aim of these studies was to attempt to define whether the type of paper and changes resulting from the passage of time and conditions of storage of documents influence Raman spectra of inks. Lines of writing executed in blue and black ballpoint pen inks and gels on sheets of paper differing in type, colour, UV and IR luminescence etc. were analysed. Three types of samples were compared: fresh (FS), stored in the dark (DS) and with access of light (LS). Samples of ink and paper were analysed by optical methods (VSC 2000 HR) and Raman spectroscopy (FORAM 684-2), comparing three groups of samples. It was ascertained that under the influence of the action of light, IR luminescence and IR absorption of some ballpoint pen inks changed; however, the influence of external factors on optical properties of blue and black gels was not observed. Raman spectra of studied writing materials remained unchanged, independent of type of paper, conditions of storage of documents, and also changes in optical properties of papers and inks themselves.
Słowa kluczowe
Questioned documents; Inks; Optical methods; Raman spectroscopy.