Abstract
The focus of this research is the stabilisation of paper with Verdigris, a green copper pigment. Due to its corrosive effects on paper, many important documents, paintings and maps are in danger. The efficiency of several commercially available deacidification agents on paper samples with Verdigris was tested, including magnesium-based Bookkeeper® dispersion, nano calcium hydroxide containing Nanorestore® and CaLoSiL® dispersions as well as a recently developed dispersion of nano calcium carbonate. The antioxidant tetrabutylammonium bromide was tested either alone or in combination with nano calcium based deacidification agents. The effect of the treatments was evaluated using colour, tensile strength, degree of polymerization and pH measurements. The results indicate that acidic degradation does not play a major role during accelerated degradation of paper containing Verdigris with moderately acidic pH value and that oxidative decay could be the main culprit of the decay. The method described, which involves the use of antioxidant tetrabutylammonium bromide in combination with calcium carbonate based deacidification dispersion, was proved to have a superior effect against degradation of paper with Verdigris in comparison to the treatments which involve deacidification agents only. Nano calcium hydroxide based deacidification agents result in high pH values of the paper samples and therefore cannot be advised for use on paper documents.
About the authors
Jasna Malešič began to work at the National and university library of Slovenia in 2001 as researcher in the field of conservation science. She received her PhD at the University of Ljubljana, Faculty for chemistry and chemical engineering in 2005. From 2005 until 2017 she was head of Conservation and Preservation department of the Library. In 2017, she joined Research and Development Division as responsible person for the preservation of library materials and researcher in the field of conservation science. She is author of several publications in the field of preservation/conservation of library materials.
Jana Kolar is Executive Director of CERIC-ERIC, a pan-European research infrastructure for characterization of materials and biomaterials. She received her PhD from the University of Ljubljana, Faculty for chemistry and chemical engineering in 1998 and has for several years lead the Conservation and Preservation department of the Library. She had published more than 60 peer-reviewed papers, and a European patent and edited two books in the field of preservation/conservation of library materials.
Mitja Denac and Bor Kolar Bačnik began attending Vič High School in 2015. They started collaborating with National and university library of Slovenia in 2017 to work on a project titled New techniques of sample preparation and stabilization of paper with pigment Verdigris under supervision of dr. Jasna Malešič, dr. Jana Kolar and Alenka Mozer. This research was very successful in competitions in Slovenia as well as in the United States, China and Luxemburg. It was also presented on many scientific events across Europe. Mitja and Bor have completed their secondary education in 2019. Mitja Denac is currently attending Biotechnical Faculty at University of Ljubljana where he studies biology. Bor Kolar Bačnik is currently studying chemistry at the Faculty for Chemistry and Chemical Technology in Ljubljana.
Acknowledgments
The authors gratefully acknowledge Gimnazija Vič for enabling Mitja Denac and Bor Kolar Bačnik to work on the science project entitled “New techniques of sample preparation and stabilization of paper with pigment Verdigris”. Alenka Mozer, the mentor at Gimnazija Vič is gratefully acknowledged for her contribution. Institute for the Protection of Cultural Heritage of Slovenia, Ljubljana is gratefully acknowledged for providing FTIR spectroscopy.
Author Contributions: Jana Kolar, Jasna Malešič were the mentors of the project, they interpreted the results and wrote the article. Jasna Malešič performed part of the analytical work. Bor Kolar Bačnik, Mitja Denac: performed the analysis, interpreted the results, and wrote part of the text. All authors read and approved the final manuscript.
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