Inside the Parchment

Even though parchment has been applied as library and archive substrate for centuries, this material’s structure and degradation patterns are less explored than paper’s ones. In this preliminary work vibrational studies highlighting distinction between parchment components are presented. Advances in conservation methods can in fact be achieved by an improved knowledge of the microscopic and spectroscopic features of the parchment components. Studies of the chemical interactions with the products used in manufacturing and writing will be presented. Standard glycine, proline and hydroxyproline FTIR spectra were compared to different kind of parchment and other collagen-based materials. Some samples were inked with different kind of inks (carbon black, iron-gall, carbon black mixed with iron II sulfate or iron-gall) other subjected to invasive treatments so as to simulate damages induced by catastrophes or by a recently developed restoring treatment. Spectral variations due to artificially induced modification of parchment were monitored and analyzed. INTRODUCTION Since antiquities parchment has been a widely applied writing support, actually the major one until the advent of paper, and still widespread even afterwards [13]. Differently from paper, however, no industrial of semi-industrial process for parchment production has ever been outlined: still nowadays parchment is only manufactured and, therefore, every specimen is unique. The lack of reproducibility is why research on parchment behavior at a structural level is still ongoing [4,13,15]. The aim of this work is providing insight about the main structural aspects of parchment and the most effective non-destructive techniques in its characterization, by means of spectroscopic analysis of several laboratory and some original samples. We also focused our study on the identification of historical inks and pigments. The manufacturing of parchment follows different procedures depending on the geographical area and historical period. The commonly intended meaning of the word “parchment” is related to the Western procedure carried out since Middle Age with extensive use of calcium hydroxide. On the other hand, different ways to treat skin, including the use of tannin and alum, led to what is today the support of many worthy documents. According to Ryder [15] the Jewish tradition is unique in finishing the parchment with vegetable tannin and oil: of course, tannin was applied in amounts much smaller than the ones needed in leather tanning. From the chemical point of view, parchment major component is collagen: this protein is constituted mainly of three amino acids (~33% glycine, 20-30% of proline and 1 9th International Conference on NDT of Art, Jerusalem Israel, 25-30 May 2008 For more papers of this publication click: www.ndt.net/search/docs.php3?MainSource=65