Atlas Coelestis, 1708, FKB 272-25 Kar, S. 18 recto

S. 18 verso

In the framework of the program forMuse the Austrian Minstry of Science and Research funded a project of the Austrian National Library in cooperation with the University of Natural Resources and Life Sciences (BOKU). The focus of the project was the degradative action of copper green pigments on paper and treatment options in conservation. Copper green pigments or verdigris have been used for coloured images in manuscripts, prints and maps from the Middle Ages to the 19th century. Copper green pigments can discolour and become brown. Copper green ions are responsible for the degradation of cellulose which results in severe mechanical damage. The paper becomes increasingly brittle.

In the conservation department preventive measures and treatment options were tested on model papers with copper green pigments. In the chemistry department of BOKU the paper samples and the effect of different treatments were analysed before and after artificial ageing on a molecular level. Among the treatments tested range the mechanical stabilisation with Japanese papers and a variety of adhesives as well as the chemical stabilisation by alkaline solutions, complexing agents and antioxidants. Japanese tissue papers with an adhesive coating were developed that can be activated with a low amount of moisture thereby reinforcing brittle papers without enhancing migration of copper ions. The complexing agent benzotriazole stabilised samples of copper green pigments on rag paper. The practical application in conservation is an ongoing project.

The scientific results are published in a first article in Heritage Science:

Kyujin Ahn, Andreas Hartl, Christa Hofmann, Ute Henniges and Antje Potthast:
Investigation of the stabilization of verdigris-containing rag paper by wet chemical treatments. In Heritage Science 2014, 2:12
Link to the article