Notch binding

Having just received the April 28 mailing I would like to confirm Harry
Campbell's observation on notch bound books.  My experience, like
Harry's indicates that when a notch bound book is opened flat the pages
separate from the notched area.  The net result is a page that is less
secure than one which has been simply double fan adhesive bound.

Though the purported reason for notching is to increase glue surface on
a page's edge and thereby strengthen the leaf attachment, I believe
(begin speculation here) the actual effect of the notches is to increase
the strength of the spine rather than the strength of the leaf
attachment.  The glue in the notches acts like small cords set into the
textblock.  These "cords" effectively add thickness to the spine.   As
the spine gets thicker its resistance to movement increases, resulting
in a stiffer book with less throw up of the spine when the book is
opened.  If this is the effect desired, I would argue that notch binding
is the worst way to achieve it.

Any extension of the spine structure into the textblock (notches or sawn
in cords) also moves much of the stress associated with opening the book
into the inner margin.  The deeper the notch the greater is the tension
placed on its innermost point when the book is opened.  Rather than the
tension being distributed evenly along the entire length of the spine
much of it is concentrated at the notches. If more notches are added the
tension is more evenly distributed.  If enough notches are added to
prevent the pages from pulling away from the notched areas when the book
is opened we have created the structural equivalent of a side sewn book
(very strong - very unusable). If we add enough notches to distribute
the tension of opening along the entire length of the spine then we've
notched away an entire section of inner margin and we're back where we
started with a straight, unnotched edge.

Increasing the strength of the spine and limiting the throw up of the
spine is better accomplished by adding linings to the spine. This keeps
the stress caused by the opening of the book at the spine layer where it
belongs rather than in the textblock where it doesn't belong.

So why do notch bindings exist (more speculation)?   My first guess is
that it is cheaper to notch a binding (accomplished in one pass by a
special notching machine) then it is to add extra lining to the spine.
Notch binding is particularly economical when it is done without double
fan adhesive binding.  These are two different processes which can be
used separately or together (a library should never assume notched
bindings are also fan glued).   Economy is further increased when the
original volume is simply notched and glued without any further milling
or removal of the original spine.

In addition to economy, notch binding is also a logical extension to
adhesive binding processes that roughen the spine for the purpose of
increasing the area of the glue to page bonding surface.  However, as
both mine and Harry's observations show, you can have too much of a good
thing.

My understanding of notch bindings leads me to believe that there is no
good reason for the use of this technique in library binding. Should
there be other perspectives or flaws in my reasoning I would be glad to
hear the other side of the story.

                                  ***
                   Conservation DistList Instance 5:4
                   Distributed: Sunday, June 9, 1991
                        Message Id: cdl-5-4-006
                                  ***