Non-invasive methods for characterisation of printed cultural heritage

The quality of a book reprint depends on several factors, e.g. paper, typesetting, reproduction of illustrations, printing and bookbinding. The quality of the 1958 and 1988 reprints of the fairytale edition from 1944 designed by the Slovenian architect Jože Plečnik was studied using standard and other non-invasive testing methods, e.g. microscopic and spectroscopic techniques, sonic velocity, Young's modulus of elasticity, surface topography and image analysis. The chemical, physical and colorimetric properties of papers and typographic tonal density were analysed. The results showed that the reprints do not correspond to the originals. Some of the differences in the reprints, if compared with the original (e.g. typographic tonal density), could have been easily avoided, while others (e.g. structural and optical properties of paper) remain unavoidable, mainly due to the influence of internal and external factors on the ageing. The ageing process influences paper properties, since optical properties deteriorate in time. It has been concluded that a precise and systematic study of the properties of an old book should be performed before the preparation of a reprint. The results of the research have shown that the applied methods are useful and satisfactory for the characterisation of the paper properties and typography, and can be of use at the analysis of printing ink and illustration reproduction.