The aroma of an old book is familiar to every user of a traditional library. This unmistakable smell is the result of the several hundred identified volatile and semi-volatile compounds (VOCs) released from the paper into the air.
The old books ought this particular smell in the degradation of the compounds and products of paper. Scientists now say that they have developed a technique which can describe the condition of an old book and tell why it has degraded, only by its odour.
They based their technique on the concept of metabolomics. Metabolism, is a process of living organisms that have the power to adapt and renew, but scientists say that the complexity of heritage objects is to an extent comparable to the complexity of living organisms, thus the “-omics” type methodologies could be effective in the study of heritage objects.
Matija Strlič and his team used this new technique called “material degradomics” to “sniff” 72 historical books and documents from the 19th and 20th centuries without altering the documents themselves. The results of gases analysis show that most paper produced between 1850 and 1990 is likely not to survive more than a century or two due to the inherent acidity autocatalyzing its degradation.
The scientists identified in total 15 VOCs; cellulose which is the most important structure element of paper and its degradation depends on its macromolecular and general environment. They also found rosin (a solid form of resin, obtained maily from pines) which is used to make paper fibres hydrophobic, and lignin, a complex aromatic cross-linked 3D polymer that has a pronounced effect on the stability of paper-based materials. Other VOCs found were gelatine – mainly in rag papers (usually linen, hemp, and cotton rags)-, aluminium and ash.
Heritage institutions, such as libraries, and museums would be very interested in this technique. A quantitative VOC analysis can be very useful as a diagnostic tool for the degradations and condition of their collectives as well as the preservation and conservation treatments.
Matija Strlič, Jacob Thomas, Tanja Trafela, Linda Csfalvayov, Irena Kralj Cigič, Jana Kolar and May Cassar. Anal. Chem., 2009, 81 (20), pp 8617–8622, DOI: 10.1021/ac9016049. ACS PublicationsImage:The astronomy library in Utrecht