Bookbinding - the process of turning the sewn signatures of a book into a coherent book block. This step occurs after rounding the back and before building up the spine. It creates spines suitable for hollow back and flexible bindings, but is not used for making rigid concave spines.

Why do it?

Backing a book is necessary for any book with a square, where the tail edges of the pages are suspended when the book is upright on a shelf. Looking at the bottom fore edge of two books, one with a square and one without, the problem becomes clear.


    No square -          |            Square
  no backing needed      |          book should be backed
                         |
  | |          | |       V          | |          | |
  |*|  pages   |*|    Gravity       |*|  pages   |*|
  |_|__________|_|                  |_|          |_|
SHELFSHELFSHELFSHELFSHELFSHELFSHELFSHELFSHELFSHELFSHELF

* boards

Over time, gravity will pull on the suspended pages. If the book is unbacked, its fore edge will slowly sag down, pulling the head of the spine apart.

cutaway view:
   _________          _________
  |_______  |        |  ___    |
  |pagespa| |        | |pag---_|
  |gespage| |        ||espagesp|
  |spagesp| |  -->   ||pagespag|
  |agespag| |        |espagesp||
  |espages| |        |agespage||
  |pagespa| |        |spagesp| |
  |         |        |   ---a| |
SHELFSHELFSHELFSHELFSHELFSHELFSHELF

The process of backing a book counters this in two ways. First, it increases the contact surface of the spine with the backing material (either the inner part of a hollow back or the flexible spine itself). And second, it beats the adhesive into the paper of the signatures, creating a solid spine.

How to Back a Book

Tools, Equipment and Materials

  • A rounded book block, sewn on tapes, cords, or with kettlestiches.
    Before backing, the spine will look like this:
           _ _
         _| | |_
       _| | | | |_
      | | | | | | |
      | | | | | | |
      | | | | | | |
      | | | | | | |
    
    
  • A hammer
    You can get special backing hammers, but anything will do. If the book is sewn on exterior cords, the striking face must be small enough to fit between the cords, but that is the only restriction.

  • Flexible adhesive, such as Polyvinyl Acetate (PVA)

  • Some sort of a clamp or bench press
    At a minimum, you can use two pieces of wood longer than your book block is tall and a couple of C-clamps. A slightly fancier solution is to drill holes in the ends of both boards and use carriage bolts or threaded rods and wing nuts to tighten them.
    Professional bookbinders use a clamp and wedge-shaped backing boards, which minimise any creases on the book block from the lower edge of your press.
    Whatever you use, ensure the surface pressing on your book is smooth.

What to Do

  1. Figure out how thick the cover boards of your book will be. Mark a line on each side of the book, parallel to the spine, 1 to 1 1/2 board thicknesses away from the back of the first signature.

  2. Line up the backing boards or the sides of your bench press along the lines you've marked. Tighten the press really tight so the book block doesn't slip out.
    side view
                ____________
               | book block |         
     |                                  |  <- press
     | o                              o |
     |                                  |
               |            |
               |            |
    
    o = attachment points for clamps or threaded rods
    
    
    top view
    
       Z                              Z 
     |                                  |  <- press
       Z      | book block |          Z 
     |                                  |
       Z                              Z
       Z                              Z
    
    Z = threaded rods (can use clamps)
    
    
    end view
                  _ _
                _| | |_
              _| | | | |_
             | | | | | | |
             | | | | | | |       
     | press | | | | | | | press |
    
    
  3. Brush the back with a flexible adhesive, like PVA. Really saturate the backs of the signatures. You'll want the paper well-softened, so that it bends easily.

  4. Start hitting.
    You want to bend the outermost signature flat to the edge of the press, the next one bent over next to it, and so on. Only the central signatures should be vertical. You'll notice that each signature widens and flattens as well as bending over, creating a smooth back.
    Use glancing blows and be gentle. Use ten soft blows rather than one hard one. There are two reasons for this. First of all, it's kinder on the book block. Secondly, it reduces the likelihood that the book block will slip down in the press, making you loosen the whole thing and start again.
    I find it useful to hold the fore edges of the book block while doing this, providing a gentle counter-pressure to the pounding of the spine.
                  _ _
                _| | |_
             _ | | | | |_
            / \| | | | | |
           (   | | | | | |       
     | press | | | | | | | press |
    
    
    then
                  _ _
               __| | |_
             _/  | | | |_
            / \  | | | | |
           (   | | | | | |       
     | press | | | | | | | press |
    
    
    then
                 __ _
               _/  | |_
             _/ \  | | |_
            / \  | | | | |
           (   | | | | | |       
     | press | | | | | | | press |
    
    
  5. Turn the press around and do the other side.
    Be sure to make the spine symmetrical. This will take practice. The final result should be something like this.
    
                __ __
              _/  |  \_
            _/ \  |  / \_
           / \  | | |  / \
          (   | | | | |   )     
    | press | | | | | | | press |
    
    

Now you can go on to cover your book, with split boards, lacing on, or casing in. This technique is compatible with both French grooves and tight joints, and is suitable for hollow backs and flexible bindings alike. Note how the cover boards fit in under the folded-over signatures to create a tidy shape.

   tight joints:             French grooves:
       __ __                         __ __
     _/  |  \_                     _/  |  \_
   _/ \  |  / \_                 _/ \  |  / \_
  / \  | | |  / \               / \  | | |  / \
 (   | | | | |   )             (   | | | | |   )
 | | | | | | | | |              \| | | | | | |/
 |C| | | | | | |B|               | | | | | | |
 |O| | | | | | |O|              /| | | | | | |\
 |V| | | | | | |A|             |C| | | | | | |B|
 |E| | | | | | |R|             |O| | | | | | |O|
 |R| | | | | | |D|             |V| | | | | | |A|
 | | | | | | | |S|             |E| | | | | | |R|
 | | | | | | | | |             |R| | | | | | |D|
 | | | | | | | | |             | | | | | | | |S|