This 1546 German translation of Pedanius Dioscorides‘ pharmacopeia, titled Kreutterbuch (literally “plant book”), has been through quite a lot.
The sewing of the existing binding was broken, the extensive paper repairs at the gutter have been eaten through by insects, many of the leaves are detached, and it has extensive staining from water damage. Pictured above is the pulled textblock, with each section separated by wide paper flags to help me keep everything organized.
Washing can be beneficial for paper in this condition by reducing staining, removing harmful products of degradation, and improving pliability of the sheet. The benefits of aqueous treatment come with a lot of risks, though. In addition to removing unwanted substances, washing can extract the original sizing. The sheet’s dimensions, surface texture, and color can be altered as well. Washing can adversely affect the inks and other applied media, so extensive testing ahead of time is essential for determining what will and won’t come out in the wash. 
After lots of discussion with the curators and spot testing, the decision was made to move forward with washing this book. The pages were vacuumed and surface cleaned to remove any soiling on the surface. After a series of baths in preconditioned deionized water, there is a significant reduction in staining and much improved legibility of the text. While in the bath, it is also very easy to remove the broken paper guards at the spine edges/folds to allow for new paper guards prior to rebinding.
Wow i can’t believe the difference. What a scary decision you guys had to make. The plant book almost looks like a work of art in it’s self. Thank you guys for preserving history. Amazing!