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Re: [BKARTS] Double-fan binding - Spine exposed by notching

It's good to finally see the name Rupert Evans appear on this list again. I should have said that my calculation of 1.33 x the area for spine notching vs none was a hypothetical calculation only. It assumed that spine notching would result in three times the area as suggested by someone else on the outside surface of the spine. It might if the notches were like a very narrow v-groove pinking scissor type cut. It is not likely that the notches are that numerous or narrow and so I agree with your calculation of much less.

I wish you or others could comment even more on the controversy about notching with double-fan gluing. There appears to be different camps developing on this list. There are the NOTCHERS AND THE NON-NOTCHERS with some people being in-between. I think some people even within companies are not agreeing on this issue. There seem to be few facts and so people are going by the Library Binding Institute recommendation to notch. Has anyone seen the tests they have done and the results?

As I mentioned previously, I have seen quite a few high volume production cold emulsion double-fan glued lay-flat books that did not have any notches. They open very flat. Other people on this list and myself have made such non notched books and they are very strong. From what I can tell, double-fan gluing without notching was used for many years since about 1930 in Europe with good results mostly with hand binding. It appears that Mekanotch came along and suggested that their notching resulted in higher page pull strengths. The Planatol machines came along and also use notching.

I would like to hear some more history on double-fan gluing. I would like to see some more facts. 

I also think that the needs of the library may in some cases be different than for production books. If huge thick volumes are being bound for libraries containing glossy stock, maybe some form of roughening at least needs to be done. If a 5.5 x 8.5 inch RepKover or Hardcover book of 0.5 inches thick is double-fan glued, absolute strength is not as important as flexibility and most of these books don't really need roughening which always introduces at least some stiffness in the binding. Am I right?

Ben Wiens...applied energy scientist
Ben Wiens Energy Science Inc.
8-1200 Brunette Ave. Coquitlam BC V3K1G3 Canada 
E-mail: ben@benwiens.com
Energy Website: http://www.benwiens.com
Read my popular web-booklet "The Future of Fuel Cells"

-----Original Message-----
I agree that the 3X figure is far too high for a double-fan-glued binding.
However, what am I missing from the calulations below? It seems to me that 3
notches, each .125 inches deep simply adds 3/4 of an inch to the length of the
spine. (.125"x6) The sides of the notch are glued, with the same or less
penetration of adhesive than the spine receives. The bottom of the notch
simply replaces the adhesion that would have occurred without the notches.
Thus the increase in glued area would be, at most 7 percent on a book with an
11 inch spine (.75/11), and 8 percent on a book with a 9 inch spine (.75/9).
    Of course the notches expose fibers to the adhesive, which should result
in a measurable increase in page pull strength, but the loss in openability is

-----Original Message-----
When double-fan gluing, isn't it the total glue area that is important? A simple sample calculation shows the following:

   1. Non notched spine side area of page exposed to adhesive = 0.004 x 11
inches = 0.044 sq inches
   2. Notched spine side area of page exposed to adhesive = 0.044 x 3 =
0.132 sq inches
   3. Paper sides exposed to adhesive = 0.010 adhesive penetration x 2 sides
x 11 inches = 0.22 sq inches

   4. Total area non notched per page = 0.264 sq inches
   5. Total area notched per page = 0.352 sq inches

So it seems that notching only increases the total glue area slightly, it
has 1.33 x the area and not 3 x the area as is often thought. One could
increase the glue penetration only slightly on the side of each page and
achieve the same total glue area. This would result in greater spine
flexibility? Maybe notching is desirable in practice because it roughens up
the paper fibers, but wouldn't just exposing the fibers be better?

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