Restoration

Consolidation of painting layer by means of sturgeon glue | © BSB/H.-R. Schulz

The Institute of Conservation (IBR) is responsible for the valuable and unique collections of the Bayerische Staatsbibliothek and other Bavarian libraries. Thus, the conservation projects mainly involve medieval manuscripts, incunabula, rare books, music manuscripts and historical sheet music, atlases and maps, as well as the personal documents of famous individuals. However, various objects from other cultures, e.g., palm leaf manuscripts, are treated as well. Professional conservation of these unique objects requires excellent skills and comprehensive knowledge of suitable methods of conservation and the ethics of conservation.

In contrast to museum objects presented in showcases, books are always subjected to a high degree of mechanical stress: A book is not only viewed from the outside, but its content, including the text and artistic design, are at the center of interest. As a result, book conservation requires us to combine conservation with usability of the book. Moreover, different objects have been impacted by different types of damage, meaning that suitable conservation procedures need to be decided upon on a case-by-case basis.

Differentially dyed fibres form the basis for optimum paper complementation | © BSB/T. Allscher

Consolidation of painting layer

In medieval book illumination, for example, different types of damage may impact the painting layer over the course of centuries. Tears, cracks or abrasion are a threat to the splendidly designed pages. The causes of these types of damage may be the painting technique, the materials, as well as external influences. To consolidate the painting layer, stability tests are first carried out under the microscope, by minimally touching the paint flakes with a very fine paint brush. If, on the one hand, the paint flakes are labile, sturgeon glue (isinglass) is applied with a brush. On the other hand, if the surface is powdery, the glue is applied in form of an aerosol.

Missing pieces in the paper

The IBR has researched and further developed a large variety of conservation techniques for paper, parchment, as well as ink and dye damages. Thus, missing pieces in the paper can be replaced inconspicuously today. For this purpose, it is key to exactly determine both the color of the paper and the size of the missing piece to be amended. Accurate color values and precise measurements of the thickness and required dimensions of the paper to be replaced allow us to produce a perfect complement of the paper based on differentially dyed fibres.

Cracks and missing parts due to ink damage are stabilised locally with an acrylate-coated Japanese tissue paper | © BSB/H.-R. Schulz

Deterioration of the parchment or paper caused by metal ions and acids in inks and paints

A further common type of damage to manuscripts and coloured pages consists in the deterioration of the parchment or paper caused by metal ions and acids in inks and paints. Such objects are particularly vulnerable where the writing is based on iron gall ink, and where paintings are based on copper-containing pigments. The parts in question become brittle and erosion occurs, while the harmful substances keep advancing into previously undamaged areas. Since moisture would further accelerate the deterioration, we developed a method in which damaged areas are laminated with an acrylate-coated, extremely thin Japanese tissue paper. Using this method, we can both prevent further ingress of moisture and stabilize the areas in danger of being lost. Following the conservation, a digital copy of the book can be produced for further use, ensuring that the original work is protected from further mechanical stress.