The Royal Commentaries of Peru (RCP) by Garcilaso de la Vega (1539-1616), published in 1688, is a large volume covering some of the history of the Incas, including their government and laws and the Spanish invasion of their countries. When received, the book showed signs of extensive use, such as well worn fore-edge corners, scratched and worn leather, broken hinges, and many old repairs. The textblock sewing was broken in places and the the textblock was in multiple sections. The binding was a tight back leather binding, so the leather rested against the spine edge of the text with minimal spine linings between the leather and paper.

Due to the PVA adhesive applied to the spine, the first section of the book was restricted from properly opening. The book was originally printed and bound with the paper grain running perpendicular rather than parallel to the spine, which was also impeding the book's function. The grain direction of the paper can affect how well the book opens and whether the pages drape or lay flat for easy reading. 

The first steps in the process of repair was removing the covers and cleaning the spine. The original leather label was carefully lifted by facing it with Japanese tissue and Klucel-G (a leather consolidant). Because the label was very brittle, the facing tissue provided the strength and stability needed to lift it from the spine.

Once the spine was cleaned, it was clear that there had been damage to the spine edges of almost all the folios. Thus, an extensive guarding project was at hand. Guarding is the process of attaching two paper leaves at their spine edges with a strip of Japanese paper and starch paste. The folios can then be sewn through the fold to reconstruct the text block.

The book is just over 1000 pages and almost every folio needed guarding. Slowly and over time, the stack of leaves became a stack of guarded folios.

The book was sewn onto cords in a pattern called "two on". Just as it sounds, two sections are added at a time and the thread alternates from one section to the other so that half the amount of thread goes through any one section. This keeps the spine edge of the book from being disproportionately larger than the fore-edge of the book, and the cords provide strength for such a large book (roughly 8.5"W x 13.5"H x 3"D). It has become much more functional for the reader as it flexes open more easily, not to mention it is in one piece again!

Read  Super Size Me: The Book Conservation Variety, Part 2 to follow the steps of sewing endbands, board preparation, and lacing the covers to the textblock.