DEGRADATION OF CELLULOSE AT THE WET DRY INTERFACE .1. THE EFFECT OF SOME CONSERVATION TREATMENTS ON BROWN LINES/

This article contains results from the study of the formation of brown lines on filter paper at the wet/dry interface with water ethanol or acetone. The effect of ageing and the effect of the conservation treat ments of washing and bleaching with the reduction agent sodium borohyd ride were investigated. Qualitative evaluation of the degradation of t he paper at the location of the brown line is done in daylight, under UV at 366 nm and staining with methylene blue dye. The results showed that any wet/dry interface, even a brief exposure, may be a potential cause of degradation. Ageing resulted in a drastic darkening of the br own line and insolubility of the brown compounds. It was also confirme d that degradation led not only to distinct compounds cleaved from the cellulose chain, but also to oxidized cellulose with new end-groups a ttached to the macromolecule. The compounds formed at the wet/dry inte rface were identified as containing carbonyl and acid groups. Reductio n with borohydride was found effective to decrease the browning of fre shly formed brown lines exclusively. Washing was also found effective only on recent brown lines and had to be done in the liquid that origi nated the brown line (water or organic solvents). Results showed that conservation processes involving local or global wetting of paper docu ments are a potential source of browning. Practical recommendations ar e given for the conservator, such as the frequent observation of paper artifacts under UV wavelengths to detect where browning could appear on ageing.