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[BKARTS] Chiming in, Reflections on double fan binding



>From: Eric Alstrom
>Maybe Peter and/or Gary can chime in too.

Okay, I'll try.

Regarding Ben Wiens speculation as to why double-fan binding has
not been widely accepted:  I believe the answer to that lies in the
ability to mechanize the process for mass production.  Hot melts
adapt very well to a mechanized, mass producing assembly line.
They go on quick and set up almost immediately.  Hot melts do not
lend themselves to the fan-gluing process and cold emulsion,
relatively slow-drying PVAs do not lend themselves well to mass
production.  The superiority of the fan-glued binding is simply
irrelevant.  The market demands fast, cheap books and the market
gets fast, cheap books.

The exception to this is the library binder (both big and small).  The
nature of the library binding business is such that every book is
potentially different from the last book and has to be handled as a
separate book.  There is no machine that accepts vastly differing
materials at one end and spews out bound volumes at the rate of
thousands per hour.  This makes library binding much more labor
intensive than edition binding.  The advantage is that the slower
overall process easily accomodates the fan-gluing process.

Regarding notching:

I am going to disagree with everyone here.  I think the perceived
effects of notching have nothing to do with the length of the glue line.
Notching effectively alters the structure of the spine as does sawing
the spine and gluing in strings.  If you took a piece of paper that was
15" long (we'll say it is 2" wide)  and added a series of little accordian
folds across the width about a 1/16th inch deep, at sufficiently close
intervals such that the length of your "accordianed"  (for want of a
better word) paper was now 10" long you will have approximated the
glue line of a notched binding with a 10" spine.  This "glue line" is 15"
(the length of our unfolded paper)  though the end to end length of the
"spine" is now 10".

Think about the accordianed folded paper in your hand.  At 15" length
it flexed easily across the width.  With the accordian folds it is now
much stiffer across the width.  We have corrugated our piece of paper
and added rigidity perpendicular to the length of the paper.  We
experience this type of structural strength everytime we use
corrugated cardboard.  Notching effectively corrugates the spine of
the book, adding rigidity to the spine.  This effect is further enhanced
by the fact that the glue tends to pool in the notches essentially
creating many small cords.  The advantage of notching over actual
cords is that the cords remain slightly elastic, the depth of the cords
can be less than actual string cords, and it is easy to add them at
frequent intervals.

As for the added length of the glue line increasing strength, I have my
doubts.  A very close, magnified inspection of the inside gutter  of a
notched binding frequently shows that with any kind of actual use of
the book, the cord of glue in the notched area has worked itself free of
the paper to which it is supposed to be attached.  This makes sense
since these  PVA cords represent a salient beyond the remainder of
the glue line which sets slightly back.  As the book opens, the opening
force can be concentrated on the tips of the notches.  However, this
brings us back to Gregor's statement that tests of notched bindings do
show improved strength (though, as I believe he pointed out, notching
is not always necessary).   So, what does notching do to add strength
if it is not the length of the glue line?  I would say it is the added
rigidity.

To understand this we have to back up and try to understand what
actually happens at the glue line.  When a fan-glued book is opened
flat there is an inevitable stress where the pages and glue meet in the
gutter.  The physics of the situation require that if you bend an object
(the spine in this case) there is going to be compression on the
backside of the bend (the outer side of the spine)  and tension or
expansion on the frontside (the gutter).  By maintaining a very thinly
built up spine you can minimize these stresses. I wrote an article
some years ago that goes into this in detail.  (The article is posted on
my website at  www.temperproductions.com/flexible_strength.htm).
At the time of  my article I concluded that these stresses could be
resolved with an "Elastic gutter" where the plasticized PVA emulsion
simply stretched across the gutter of my thin-spined binding.  Several
years later, with the added analytical benefit of an old dissecting
microscope on long term loan to me from the St. Bonventure
University biology department, I came to reject my earlier conclusions.
With my vision enhanced by 30x magnification I saw that there was
insufficient PVA between the pages to stretch across the void formed
when the book fully opened. However, the bindings I designed and
built on my earlier suppostions generally were very successful, with
the exception of some coated papers. Somehow the stress was being
relieved.

Further observation showed that the stress of opening a book flat
almost always leads to some structural failure.  With uncoated papers
the structural failure is generally benign, whereas with coated papers
the failure weakens the page attachment to the point where further
failure is more imminent.  Uncoated papers suffer from structural
failure of the substrate (the paper) itself. The paper will actually split
and feather out along its length to make up the extra thickness
required of it when the book opens flat to the gutter margin.  The bond
between the adhesive and the paper remains intact.  Page pull
strength remains high.  The page is essentially broken in and ready
for continued use.

Whereas substrate failure tends to be benign, adhesive failure is less
so.  With uncoated papers   the bond between the pva and coated
paper is stronger than the internal bonds of the paper itself.  With
coated papers this is often not the case.  The adhesion between the
pages fails before the internal bonds of the paper itself.  I characterize
this generally as adhesive failure though the problem is frequently not
the bond between the glue and the paper, but the bond between the
coating on the paper and the paper itself.  The glue will usually
remained attached to the coating.  The coating will simply detach from
the paper.  Whether the adhesion fails between coating and adhesive
or between coating and paper the effect is the same, the pages at the
opening are left without the line of glue between the pages that gives
fan-gluing its strength.  Page pull strength  drops off dramatically and
failure of the page attachment is more likely.

So what does this have to do with notch bindings and rigidity?  As you
stiffen the spine you inhibit the full opening of the book.  This prevents
the attachment between the pages from reaching a breaking point.
With this knowledge in hand I learned that I could increase the page
pull strength of coated papers significantly by controlling the spine (I
have numbers but it is Saturday night and this isn't supposed to be a
research paper) .  The amount of control needed depended on the
drape (the flexibility) of the paper.  Conversely,  I found that I gained
little or nothing by stiffening the spine of books with uncoated paper.
Page pull tests (like Ben, I built my own tester) remained comparable
for a flat-opening, uncoated-paper book and a uncoated-paper book
with a more controlled opening.

Notching is simply one means of controlling the spine.  The spine can
be controlled in many ways, some good (notching probably falls in this
category), some horribly destructive (remember all those perfect
bound books that broke in your hands when you first opened them).
But this a topic beyond my energies this evening.

I'm hoping the above makes sense (it's late and I hope I'm not
babbling).  These are my ideas and subject any to withering criticism
anybody would like to throw at them.  I hope to get the above in
illustrated form on my website in the not too distant future and will
post to the list when I do.

                                        Pete Jermann

                                 Pete Jermann
TeMPeR Productions
117 South 14th St.
Olean, NY 14760
Tel. 716-373-9450
Email: pete@temperproductions.com

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