Leather is an ideal material for bookbinding due to its strength and flexibility as well as its receptivity to decoration, such as tooling or stamping. Depending on the tanning method (how the leather is treated once harvested from the animal) and what kind of environmental exposure it has endured, leather may last for centuries.

When leather is used in a bookbinding, one of the common areas it can fail is at the hinge of the book where the front or back cover is connected to the spine of the book. Since the cover flexes in that area, the leather may crack or split over time. 

There are several different methods for reattaching the covers on leather bindings. This method was chosen because this book was a tight back binding, meaning that the spine of the cover is directly adhered to the spine of the textblock. This is opposed to a hollow back binding, in which the spine of the cover flexes away from the spine of the textblock (it is not directly adhered). In a tight back binding, it is sometimes very difficult to lift the leather away from the textblock beneath because the leather is often quite brittle when it is older.

Since this book was a tight back, the leather was brittle, and it is a larger book with heavier covers, I chose to reattach the covers by piercing the spine. This is a more invasive version of board reattachment that I might have avoided for a more rare or otherwise special book. It is not ideal to pierce through the leather, but it does create a very strong attachment and can be disguised aesthetically with toned Japanese paper.

First, I opened the textblock to the center of the first signature (signatures are groups of printed sheets folded in half, one inside the other). From there, I inserted a needle vise into a pair of sewing holes and out through the spine. I inserted thread through those holes to create a "U" shape through the spine with the ends extending outside the book. I repeated this step at another pair of sewing holes inside the same signature so that the board would be reattached from two locations along the spine.
     
I was able to carefully lift the leather from the board along the spine edge of the book covers. After trimming to the right length, I frayed the ends of the thread or cord so they could be splayed out and would lay flatter once adhered to the cover between the leather and board. Then, I applied adhesive to reattach the leather to the board with the frayed cord sandwiched in between. This method provides a much stronger attachment than just a bridge or patch of Japanese paper along the hinge. However, the Japanese paper was added afterward as an added layer of strength and to disguise the mend. A patch of toned Japanese paper was also used on the inside of the cover along the hinge.

All of the above steps were performed on both the front and back covers.

 A very special thanks is due to conservator Jeff Peachey for his workshop I attended on Leather Board Reattachments at Emory University Libraries' Preservation Lab in November, 2018.