Characterization and degradation pathways of ancient Korean waxed papers

The annals of the Choson dynasty, a group of archives including 2077 volumes dated from 1392 till 1863 were declared National Treasury by the Korean government in 1973 and were later registered as Memory of the World by Unesco in October 1997. Some of these historical papers, coated with a wax substance, are called Korean wax papers. They present nowadays various patterns of degradation. As little is known about the waxes used and the techniques employed to wax the papers, it appeared necessary to identify the substances used and to assess their degree and pathways of alteration to further define adapted conservation treatment and preservation conditions. We focused in this paper on four microsamples taken from different waxed Choson manuscripts dated from the 15th and 16th centuries. A modern Korean beeswax sample was also analyzed as reference. A two-step analytical methodology based on infrared spectroscopy, HT-GC and HT-GC/MS analysis was developed. These investigations led to the identification of beeswax in all the samples. In a single sample, paraffin was also determined, indicating a step of restoration, possibly during the 19th century or afterwards. All the samples revealed an altered pattern of beeswax that is reported here for the first time. Particularly, the presence of hydroxyesters in high amount and the formation of n-aldehydes are new and interesting results that may be explained by the use of previous oxidative treatments. Depletion of the shortest chain n-alkanes and monoesters was also observed. The different alteration pathways of beeswax in Korean wax papers are fully discussed in this paper.