Board Slotting


Since the 1960’s several different methods have been developed to deal with the joint failure and board detachment issues that often occur to leather-bound volumes, and each offers distinct treatment outcomes in terms of strength, aesthetics, and disruption of the original binding material. Conn (1996) provides brief, but clear descriptions of a range of these techniques in her feasibility study on treatment options for circulating collections.  In the late 1970’s, Christopher Clarkson developed a method of reattaching book boards in which a slot is cut into the board to accept a flange of textile that is attached to the spine of the textblock. He presented a paper on his method at the Institute of Paper Conservation conference in 1992. This technique offers some distinct advantages over others, including that the turn-ins, pastedowns, and covering material are not disturbed. The thickness of the board is also maintained, unlike the usual swell resulting from a traditional leather reback. This can be beneficial in cases where the leather covering the board is highly decorated or chemically degraded (Zimmern, 2000 , p. 24).

Zimmern states that board slotting with a normal milling machine is “complicated and time-consuming” (p. 22) and, as a result, at least three machines have been developed in recent years to increase the speed and accuracy of the process. We are fortunate to have one of Jeff Peachey’s board slotting machines here at NBSS (seen below) and last week Lou DiGennaro, NBSS alum and Assistant Conservator for Special Collections at NYU libraries, came up to Boston to demonstrate the setup and operation of the machine. I’ll share a few photos and an extremely brief writeup of the workshop here. If you would like to read more on the topic, please see the bibliography at the end of the post.

During his demo, Lou discussed Clarkson’s, Peachey’s, and Alan Puglia’s structures (described below) for board reattachment in instances where the spine material is still intact, as well as the method described by Angela Andres (2008) for books missing their spine covering. No matter the method, the spine of the book is first cleaned and consolidated with paste and Japanese paper and the leather at the board edge consolidated with a 2% Klucel G in ethanol solution.

Lou first went over the basics of the machine’s setup and operation, including setting the carriage angle, blade height, depth of cut, and speed of operation. He also discussed choosing a thickness of saw blade based upon the thickness of the board and flange material to be inserted. Changing the blade and setting up the machine went very quickly. You can find Peachey’s short video on machine operation here.

The book board is placed face up in the carriage (here with a waste board on top) and the height of the blade set to just under the covering material.

Before slotting, the alignment of the blade is checked at both the head and tail to ensure that the slot would be even across the length of the board. The saw motor is then activated, the carriage cranked in so that the blade is cutting a 5-8 mm slot, and the carriage set in motion. The slot is started and stopped just inside the edges of the board so that the turn-in material is not disturbed. Hopefully the image below is clear enough to illustrate.

Both boards were slotted in the same fashion. After tapping out a small amount of sawdust and gently clearing the slot with a micro spatula, the front board is placed in a finishing or lying press. Lou used a small syringe to inject a bead of PVA into the slot.

Previously, Lou had created a two-part hinge, consisting of a layer of linen or cotton backed with Kizukishi or Sekishu and a layer of pre-toned Moriki lined with Kizukishi. The two hinge layers were tipped together on one side with PVA and inserted into the slot. [As a related side-note,  Zimmern’s article provides an interesting discussion of the folding endurance of three hinge materials and three kinds of adhesive.]

After nipping the board and allowing it to dry under controlling weight, the textblock was aligned on the board and the spine glued up. Lou pulled the first hinge layer firmly around the spine and worked it down with a bone folder.

Next, just the shoulder of the hinge was glued and the second hinge layer wrapped around, worked into the shoulder, and allowed to dry under weight. This creates a natural hollow.

After trimming the resulting flange to the slot depth, Lou injected PVA into the slot in the back board…

… aligned it on the textblock, and inserted the flange with a micro-spatula.

Once again, the board was nipped and allowed to dry under weight.

In the last step, the original spine piece was adhered onto the new spine hollow. After delaminating a few of the layers of paper inside the original spine piece, Lou adhered it to the outer (Moriki) hinge layer.

After working it down with a teflon folder, he then wrapped the volume in a compression bandage and placed it under a light weight to dry.

Lou also brought along an example of board slotting on a book that had lost its spine covering entirely. In this example, the boards were slotted all the way through the turn ins and the new spine material was turned in to form the endcaps.

The inside hinge is repaired with a strip of Japanese tissue toned to match the endpapers.


At the end of the demo, a few of us were able to try the machine out on our own. Peachey’s machine is incredibly easy to set up and use. Even without any previous board slotting experience, I was able to successfully slot a moderately thin board on my first try. While this machine may not be an economical option for the average conservator in private practice, it does present a viable treatment option for institutions with collections of circulating or medium-rare nineteenth century volumes with board attachment problems. By prepping hinge material in advance and batching treatments, a technician could probably become very quick with these repairs.

As I said, this is an extremely cursory look at board slotting and there is a lot of fantastic material out there on the subject. Including the list of articles below, I’d suggest a blog by Jeff Peachey, Victoria Stevens, and several other contributors (found here) centered around board slotting that deals with a range of topics and links to the relevant academic literature.


Andres, A. M. (2008). A new variation on board slotting: Case binding meets in-boards binding. The Bonefolder, 4(2), 24-26.

Clarkson, C. (1992). Board slotting: A new technique for re-attaching bookboards. The Institute of Paper Conservation Conference Papers, Manchester.

Conn, D. (1996). Board reattachment for circulating collections: a feasibility study. Book and Paper Group Annual, 15, 29–40.

Minter, B. (2006).  A variation on the board slotting machine. In M. Kite & R. Thomson (Ed.), Conservation of leather and related materials(pp. 241-242). Oxford, UK: Butterworth-Heinemann.

Peachey, J. S. (2006) New possibilities for board slotting. The Bonefolder: an e-journal for the bookbinder and book artist, 2(2), 28-32.

Simpson, E. (1994). Setting up a board-slotting programme. The Paper Conservator, 18, 77-89.

Zimmern, F. (2000). Board slotting: A machine-supported book conservation method. The Book and Paper Group Annual, 19, 19-25.


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