Academic thesis
| Edwina Erner: | Bleaching of microbially induced discoloration of paper. | back |
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| Abstract: | In the conservation and restoration of paper objects local discoloration is a common problem as a result of mold infestation. These discolorations are complex metabolites, which can spoil the esthetic appearance of the objects. When restoring the paper a bleaching treatment is applied to remove or respectively reduce this discoloration. This master thesis deals with the application of reductive and oxidative bleaching methods and their effects on microbially induced discoloration. A series of experiments shall show prove of the Maillard reaction as it is a possible cause for the phenomenon of the “colour-reversion” after a bleaching treatment or not. The Maillard reaction causes characteristic discoloration as a result of a heat induced reaction between an amino acid and glucose. Free amino acids, among others pass through a microbial infection in the object. In the practical part of the thesis dyes of Cladosporium herbarum and Aspergillus versicolor are extracted and applied to Whatman paper and historical rag paper. In addition artificial Maillard products are generated on paper samples. The samples are first bleached with sodium borohydride and hydrogen peroxide, and then evaluated by means of using a colorimeter. |
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