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Author's note:  I wrote this about 14 years ago.  As time passes so do ideas and understanding.  If I wrote this today it would have more qualifications and a much greater expansion on what exactly happens at the glue line. My conclusion, shown in figure 6 regarding the elastic gutter joint is simply wrong. I would encourage you to read my "Reflections on Book Structures" to see what really happens in the gutter joint. That said I believe there is sufficient food for thought that this article remains worth reading.  The binding discussed herein has had thousands of iterations as bound periodicals and monographs in the university library where I worked.  It has been a very successful binding, particularly with uncoated papers.  Minor problems (single page failures) with uncoated paper have lead to further experimentation, improved success, and ideas that I have expressed in my "Reflections" articles. (7/9/08)

Flexible Strength:

The adhesive Quarter-joint binding

by Pete Jermann  (Originally published in New Library Scene, August 1994)

Fig 1.

Polyvinly acetate (PVA) adhesives have largely replaced sewing as a means of leaf attachment in modern library binding. PVA adhesives not only secure one leave to another but introduce signficant elasticity at the point of leaf attachment. The elasticity provides a dynamic that suggests a binding strategy entirely different from that used for sewn books. The adhesive quarter-joint binding, described in this paper, attempts to maximize the benefits of this elasticity by combining flexible and elastic modern PVA adhesives, strong thin spine linings, a redesigned endsheet and an appropriate casing technique to create a book that opens perfectly flat (figure 1). This ability to open flat, in turn, effectively neutralizes many of the problems normally associated with the binding of heavy papers or cross-grain papers. The adhesive quarter joint binding is suitable for leaves that range from normal book paper, to heavier paper stocks, to board or any combination thereof. It is particularly suitable for heavier papers and books of mixed paper weights, such as journal accumulations bound together with their heavier covers intact. In the adhesive quarter-joint binding I have tried to achieve a binding that is at rest on the shelf and in use. This state of rest distinctly contrasts with the near perpetual state of stress found in traditional bindings. 

The possibilities inherent in an adhesive bound quarter-joint binding require an understanding of strength and stress in bookbinding and the modifications necessary to achieve an ideal combination of the two. In the ensuing essay I submit my understanding of these topics, how they relate to a book's structure, the construction of adhesive-bound quarter-joint binding and how it resolves the stress and strain found in traditional binding.

Absolute vs. Relative Strength

A book breaks down when stress exceeds strength. A book's strength is not a constant but a value that tends to decrease with time and use. At some point in time stress exceeds strength and damage occurs.

We can measure strength in absolute or relative terms. The strength of a book's leaf attachment is traditionally measured with a page pull test. This test simply exerts an ever increasing pulling force on a single page within a book until the page separates from the book. The measure of the force in pounds or kilograms required to separate the page from the book is a measure of the absolute strength of this attachment. Our initial inclination is to regard higher ratings as good and lower ratings as less so. A book whose page attachment offers the highest pull rating will always be less likely to break down than a book whose pages are more readily detached. The equivocal truth, however, is that it depends. It depends on the overall structure of the book. 

Relative strength measures strength in the context of the environment in which that strength exists. The oak tree and the blade of grass provide a natural example of the concepts of absolute and relative strength. The oak tree stands firm and resistant in a stiff wind. It will give within limits, but once the wind exceeds those limits it will uproot or break. A blade of grass in the same wind will simply yield. Should the wind persist it will bend flat to the ground and let the wind pass. When the wind stops, the blade of grass will resume its former upright position. Nobody doubts that an oak tree is stronger than a blade of grass, yet the ability of the grass to reduce its profile to the wind allows it to minimize the stress of the wind and survive the storm without the strength of the oak. A book can be like the oak tree. Just as the oak tree will only lie flat after it has broken, so only by breaking will the book succumb fully to the photocopy machine. A book, however, can also be like the blade of grass. Just as the grass gives to the wind so a book can give to the photocopy machine. The strength of the first book is unmatched by the second book - yet one survives and one doesn't.

Relative strength recognizes that the stress on a book varies with a book's structure. A page that can resist up to 15 pounds of pull is useless in a book that exerts 20 pounds of pull when the book is opened. That anybody would design such a book seems inherently ridiculous. The reality, however, is that we have all experienced the "perfect" binding whose pages break loose with the first opening. In these bindings the strength of the page attachment is less than the structural stress exerted by the book's opening. Another book could have pages capable of resisting only 10 pounds of pull. If the opening of the book, however, only exerted one pound of pull on the pages, the strength of the page attachment would be more than adequate by a factor of 10. The concept of relative strength recognizes that the latter book is more durable than the former even though the absolute strength of the page attachment is less.

Relative strength is the ratio of absolute strength over stress. If the ratio is one then stress and strength are equal and the book will be stable only until an increase in stress or a decrease in strength occurs. Where the ratio is less then one, as in the first example above (15 lb. strength/20lb. stress = .75), the book will fail. In the second example the ratio of 10 (10 lb. strength/1 lb. stress) allows a wide latitude for increase in stress or decrease in strength. The higher the ratio the more likely the book's survival. This statement assumes several arguable premises which I will state as fact for the time being. These premises are: 1) the major stresses on a book at the point of leaf attachment are inherent to the book's structure, and 2) unless a page is willfully removed, page separations are usually the result of internally transmitted stresses that overtime have either weakened page attachment or damaged the book's structure such that stress becomes concentrated at the point of leaf attachment.

Improving book design based on absolute strength means increasing the strength of the component parts. Improving book design based on the concept of relative strength gives the designer two paths. He/she may increase the strength or decrease the stress inherent within the book structure. A move in either direction can increase the relative strength of the book. Whereas much has been done with traditional bindings to increase their absolute strength, less has been done to decrease the stress. My quest was to follow the latter path.


The Stressed-out Book

Unless lying closed on its side, the traditional hard bound book is in a constant state of stress. This stress begins when the book is first shelved. The practice of squares on the bottom edges of a book cause the textblock to hang from its case when the book is standing upright. A square is the slight extension of the book's cover beyond the textblock on the top, bottom and front edges. The inclusion of a bottom square lifts the textblock off of the shelf and places the weight of the textblock on the joints where the cover meets the spine. Under such circumstances the textblock tends to lurch forward out of the case. This tendency can be counteracted by lining and reinforcing the spine to help it maintain its shape (increasing the strength) and by rounding and shaping the spine to help lock it into the case. Over time, however, the spine will lose its shape and the joints will tend to loosen.

When the book is removed from the shelf and laid open the very liners that reinforce the spine in its vertical shelved position create a structure resistant to the book's opening (fig. 2 and fig. 3). The glue and other materials that may line the spine (cloth, paper, cords, tape, leather, etc.) create a laminate structure whose tendency is to hold the original convex shape in which it was formed. This laminated structure resists the natural tendency of the pages to open to a flat or gravity neutral position (the curvature to which the pages would naturally fall if not attached to the spine). With traditional materials and techniques the resistance of the spine is desirable. Traditional hide glues of limited flexibility dictate a spine of limited mobility. The use of sewn-on cords and tapes to secure boards to the textblock not only inhibit the motion of the spine but demand limited motion to protect the tapes, cords and sewing. These structures require that a quality book open such that the spine rises slightly in a gentle concave arc (as depicted in fig. 2). A spine that breaks this pattern and opens into an inverted vee not only threatens to stress the glue beyond its elasticity but also puts undue stress on the sewing, the cords and the leaf attachment. 

When a book is opened the pages tend to rise toward a flat or planar position at the point of opening. This creates an upward pull (A). As the book rises at the point of opening there is a corresponding movement (C) of the joints (the junction of the textblock spine and the case) toward the center. 

The spine on the traditional case bound book contains two

  laminated structures. The layers on the spine of the textblock composed of the glue, super (and/or cords, tapes, etc.) and paper liner(s) make up one laminated structure. The layers on the case spine made of the cover material (cloth, leather or paper), the inlay (a piece of heavy paper or bristol), and the cover material turn overs at the head and tail of the book make up the second laminate structure.

It is the nature of laminated materials to retain the shape in which they were formed and to resist changes to this original shape. The laminated spine of the textblock whose original shape is convex, resists (B) the upward pull of the pages. The case spine resists (D) the inward pull (C) of the textblock joints.

Fig. 2

A book that opens in a gentle arc indicates a proper resolution of forces. The problem inherent in such a binding, however, is implied in the very phrase resolution of forces. Such a binding is indeed a resolution of conflicting forces. It is a resolution much like two rams butting heads with equal force. Though each ram may be pushing with all his might it may appear the rams are simply standing head to head. Such is the illusion of the traditional book. The gentle concavity of the spine is not a book at rest, but a momentary resolution between the upward thrust of the pages and the resistance of the spine to any change in shape. The upward thrust of the pages is caused by the individual pages pulling at the point of leaf attachment as they try to achieve a state of rest. Just as the resistance of the spine can vary with different types of linings and sewing constructs, so can the upward thrust of the pages vary with the type of paper. Stiff or cross-grained papers exert greater pull than papers that drape well. Papers that don't slide easily across one another, due to cockling, static induced adhesion or other factors, will tend to have a cumulative effect that can exert a significant pull on the pages at the center of the opening.

A
B
C

The illustrations above represent books made of binder's board to illustrate the effect of linings on the textblock spine. Each book was allowed to fall open without the leaves being forced flat. 

A) 1 cotton liner - book falls into a fully open position.

B) 2 cotton liners - book resists opening flat 

C) 1 cotton liners, 2 100 lb. paper liners - increased layers add increased resistance to opening

Fig. 3

 

Whereas convention esteems the book whose spine opens to a gentle concave arc, it conversely disparages the book whose spine opens to an inverted vee (fig. 4). The former opening distributes stress, the latter concentrates it, often with damaging results. Given the traditional cloth and paper (and cords or tapes) laminate such indeed will be the case. An inverted vee opening has two effects (fig. 5). First it damages the laminated spine structure by causing a delamination at the apex of the vee. This delamination usually occurs within the paper liner rather than between the paper and cloth liners and becomes a weak point in the spine's structure. This weakness will exhibit itself as memory point to which the book will readily fall open. Secondly, the fold at the vee's apex represents a doubling of the paper-cloth laminate which tends to pull the pages apart at that point. In a sewn book this tends to pull on the sewing local to the point of stress and contributes to its loosening. 

Fig. 4

We can inhibit the motion of the spine by strengthening it with stronger or additional reinforcing materials. This very strengthening, however, increases the potential for damage when the book is actually used. The thicker the laminate or built up spine structure the greater the damage to the book should the spine be forced into a vee shaped opening (as is likely to happen when photocopied). Anything that adds to the effective thickness of the textblock spine, such as tapes, sewn on cords, oversewing, sidesewing, notch binding, or particularly deep fan gluing, limits the movement of the spine and increases internal structural stresses. A method such as side-sewing, where a book is sewn through the gutter margin, creates an effective spine thickness of 1/4 to 1/2 inch and limits the motion of the spine absolutely. The strength, both relative and absolute, of sidesewn bindings is substantial but the cost of that strength is a high degree of inherent stress. This stress manifests itself in the need for great external force to keep the book open for reading or the frequent full body press placed on such a book at the photocopy machine. 

Spine Linings and the Flat Opening

The liners which make up the layered spine affect a book's ability to open flat. A properly lined spine will allow a book to open flat without structural damage. The photo illustrations to the right are closeups of books made of binder's board. These board books were purposely made to exaggerate the stress of opening to clearly show the effect of the number of layers or of the thickness of the structure lining the spine.

A) 1 cotton liner - the book opens flat without being forced. The spread between the two open halves is minimal.

B) 1 cotton liner, 2 100 lb. paper liners - the book had to be forced into a flat open position. The spread between the two blocks becomes wider with the edges of the board beginning to pull away from the cloth liner. Though not visible in the photo, the paper liners have started to delaminate.

C) 1 cotton liner, 4 100 lb. paper liners - the book had to be forced into a flat open position. The spread between the two blocks is such that one board is almost completely detached by the act of opening the book. The liners quite visibly have begun to delaminate under the stress of opening. Though books are seldom so heavily lined, the impact of a sewn on raised cord would be similar or greater.

A

B
C

The action of the book's cover or case further exacerbates the stress found in the interaction between the laminated spine structure and pages. Should the book be a tight back design, the covering material (usually leather) adds another layer of lamination to the spine and increases the aforementioned effects. a modern hollowback design adds different stresses. The spine structure on the case consisting of the cover material, the inlay, and the cover material's turnovers creates yet another laminated structure resisting change. this structure effectively keeps the outer boards from moving toward each other as they are wont to do when a book is opening (fig. 2). This resistance creates a pulling on the joints where the cover is attached to the textblock and a pulling across the paper-cloth laminate on the spine of the textblock. The pulling on the paper-cloth laminate further inhibits the motion of the textblock spine, further preventing the pages from reaching a state of flatness or a position of rest. These combined stresses can cause a loosening of the joints and/or delamination of the inlay from the cover material.


The Solution

Traditional bindings deal with stress through strength. A well executed traditional binding is strong, durable and suitable to its intended purpose of reading. Today, however, we no longer merely read our books. We subject them to photocopiers, microfilm cameras and digital scanners. Whereas normal reading seldom requires a perfectly flat page, these modern technologies often do. Fortunately, modern materials also give us the means to bind a book that will not only meet the needs of both human and mechanical readers but will also allow us to significantly reduce the internal stresses found in the traditional book. We can design a book that is largely at rest both on the shelf and in use.

Standard methods of strengthening are appropriate for the traditional book that is made of signatures, sewn through the fold, glued, lined with cloth and paper, and covered with a hollowback case. Should such a book open completely flat both the signature at the point of opening and the hinge joints are stressed. A structure that limits the motion of the spine to a gentle concave shape prevents this undesirable concentration of stress. Modern bindings composed of single leaves, rather that signatures, and secured with flexible and elastic adhesives are different animals with different strengths and different weaknesses. An adhesive binding can be designed such that the pages lie completely flat when opened. Furthermore, we can virtually eliminate the damaging structural stresses associated with such an opening. Modern adhesives allow us to increase the relative strength of a binding by removing stress rather than increasing strength.

The key to reducing stress begins with the ability of a book to open flat without concentrating stress on the point of opening. In a hollowback sewn book whose textblock spine is lined with both cloth and paper liners, two factors contribute to the stress at this point of opening: 1) the structural dynamics of the laminated spine composed of a paper liner, a cloth super and the back of the signatures which effectively create another layer of paper, and 2) the pulling action of the case on the spine liners.

The solution to the problem presented by the laminated spine is to reduce stress by reducing the laminations or thickness of the spine structure. This can done in two stages. The first stage eliminates the paper layer created by the backs of the signatures by converting to a binding made of single leaves where the leaves are secured with a properly plasticized PVA. Rather than a continuous expanse of paper crossing the gutter joint, we can now have two individual pages joined at the gutter by an elastic emulsion. This emulsion can stretch to accommodate the slight expansion of the gutter required for a full flat opening and then return to its original dimensions when the book is closed or the page is turned (fig. 6). 

The Elastic Gutter Joint

The full, flat opening of a book causes the gutter joint to spread at the point of opening. When a book is made of single leaves joined with an elastic PVA adhesive, the adhesive (the gray in the enlarged area above) can stretch across the gutter joint as shown at point A. The super (B) unhampered by tapes, cords or a paper liner, simply folds back on itself.

Figure 6

The elasticity of the emulsion is limited, however, and can be stressed beyond its limit. The laminated spine structure exerts a spreading force on the gutter as the traditional concave spine action gives way to the inverted vee. The thicker the laminate the greater this tendency. In the second stage of our solution we further reduce the thickness of the laminate. We eliminate the paper liner completely and, instead, rely on a strong, thin (the thinner the better) cloth liner or a liner made of a synthetic material such as polyester. Eliminating the paper liner reduces the thickness of the spine structure and allows the spine to move more freely.

The pulling action of the case on the textblock spine represents the final source of stress on the page attachment of the opened book. Redesigning the case so the case spine moves freely and does not resist the opening of the book, eliminates this stress. This is accomplished by broadening the hinge joint on the book's cover to at least 1/4 the thickness of the book and leaving these joints unattached to textblock (see fig. 1)2.* Not only do the loose joints allow for free movement of the spine, they also allow the use of an inflexible inlay in the case spine. This rigid inlay provides a good base for the use of paper labels which tend to crease and delaminate on flexible case spines.

At this point, if the adhesive is sufficiently elastic, if the spine is lined with a thin flexible and strong material and if the case offers no resistance to the opening of the textblock, the book should open such that the pages lie flat. As the spine gives completely to the upward thrust of the pages, the pages neither fan open nor pull where they attach to the spine. Rather than the collective stress of many pages attempting to achieve equilibrium, our redesigned book reduces the pull to that of the two pages on either side of the glue line and resolves this minimal stress through the elasticity of the adhesive. 

To complete our design we must deal with the problems associated with the book standing on the shelf and in transit. The use of squares, as described earlier, creates a situation where the textblock is suspended in the case when a book is vertically shelved. So suspended, the textblock both pulls on the hinge joints and deforms at the spine and foredge as it tries to come to rest on the shelf. A traditional binding counteracts this with a slightly stiffened, reinforced spine, secure hinge joints and a rounded and shaped spine. none of these characteristics are found in our adhesive QUARTER-JOINT binding. We can solve this simply, however, by reducing the squares on the bottom edge of the case such that the textblock can rest on the shelf without straining its attachment to the case. This will remove all or most of the strain on the standing book. A smaller, residual strain on the hinge joints will sometimes exist due to the difficulty of perfectly aligning the textblock with the bottom edge of the case, as well as problems associated with the forward pitch of larger textblocks if the book is loosely shelved. The solution to this problem is the same as the solution to the problem posed by a book in transit.

The Stiff Shoulder Joint

Since the quarter-joint book's cover or case is not joined to the textblock at the hinge joint, as in traditional bindings, an alternate structure is provided to prevent the textblock from falling forward in the case when the book is carried or loosely shelved. A stiffened endsheet provides this support. The diagram above shows a standard, commercially available endsheet comprised of a folded sheet and a single sheet secured together with a cambric strip which extends about an inch onto the pastedown and about 1/4" onto the flyleaf. This standard endsheet is stiffened by gluing a 5 to 10 mil polyester stiffener (mylar) into the gutter margin of the folded sheet which is then glued closed. This creates a single laminated pastedown comprised of the opposing sheets of the folded sheet and the stiffener. It is important that the stiffener be slightly flexible and resistant to creasing as once it is creased along the joint it will no longer adequately support the textblock. A strip of 5 or 10 mil mylar or an equivalent serves this purpose well.

Figure 7

When in transit, a book with loose hinge joints will tend to drop out of the case, particularly when carried in one's hand with the foredge down. A stiffening of the endsheets in the hinge joint area counteracts this problem, as well as any slight forward pitch of the textblock that remains even when the bottom case squares are eliminated. On small, light weight books this stiffening occurs naturally if the spine lining cloth that passes over the spine and is secured to the endsheets is of sufficient weight. Heavier books require an endsheet reinforcing material that offers some flexibility yet a high resistance to creasing. For lack of other available materials, I have found that 5 to 10 mil Mylar offers these capabilities. After a period of trial and error I have arrived at a solution based on a modified commercially available endsheet (fig. 7). Once the endsheets are properly stiffened the completed binding can be handled without any sense of a freely moving textblock. 

Caveats and Conclusions 

With every advance into new territory there are possible pitfalls. The adhesive bound, loose quarter-joint binding depends on the quality and longevity of the adhesive used. Its long term survival requires that the emulsion formed on the spine remains elastic and the adhesive bonds durable. Unlike a traditional sewn binding where the sewing provides a fallback once the adhesives on the spine break down, the adhesive bound quarter-joint binding has no such fall back position once the adhesive fails. However, if this problem did occur and was caught before the book became a mess of loose tattered paper, rebinding could be easily accomplished. Though my experience to date has indicated adhesive quarter-joint bindings are durable, I continue to search for a better adhesive and a better spine lining material.

Whereas the page pull strength of a sewn binding is the strength of the paper, the page pull strength of an adhesive binding tends to be that of the adhesive. Pages can be peeled from the quarter joint binding with less effort than they can be torn from a sewn binding. The absolute strength of the page attachment is low compared to traditional sewing methods and some other adhesive methods. I would maintain, however, that the relative strength is high and that this high relative strength is more than sufficient for normal use. Abnormal uses, such as willful removal of pages, usually introduce strains which exceed the strength of the paper and render the strength of leaf attachment irrelevant.

The action of the loose quarter joint binding differs from that of traditionally bound books. as the reader moves from one point in the book to another, the case spine moves to adjust to these changes. in large, heavy books (1-1/2" to 2-1/2") these adjustments noticeably raise and lower the textblock when the book lies open on a table. Occasionally the case spine catches under the weight of one side of the book and requires some adjustment to bring the textblock back into a state of equilibrium. On smaller volumes this movement of the case spine is not particularly noticeable. 

To date these problems appear minor. I have submitted hundreds of adhesive bound quarter-joint bindings to the rigors of use in the real world of an academic library. Over the past year I have purposely selected books for their high usage. I have bound the quarterly issues of the Reader's Guide and the quarterly accumulations of heavily used periodicals such as Time, Newsweek, Forbes, Businessweek, Psychological Abstracts, etc. I have pushed the limits beyond thicknesses and weights I normally bind to include volumes up to 2-1/2" thick. I have particularly selected volumes with coated papers. The results so far are promising. The quarterly supplements of the Reader's Guide have survived, somewhat tattered, but still intact when the annual cumulation arrived up to a year later. I have encountered several instances of loose pages in the bound, coated paper, periodical volumes. In most of these cases the problem could be identified as pages that slipped forward in the initial gluing process and were insufficiently attached from the beginning. Of the remaining (2 or 3) the page failure rate appears to be less (though I am honestly only guessing) than the page failure rate in earlier, more traditional fan glued bindings. Several volumes of USA Today, a news magazine (not the daily newspaper), printed on stiff coated paper, had failed in their previous tight backed, quarterbound bindings (fan-glued, with cloth super and F grade buckram glued directly to the spine). To date, the quarter-joint rebindings have survived approximately a year with no sign of failure.

Whereas the problems appear minor the advantages of the adhesive bound quarter-joint binding are significant. First, photocopying no longer threatens the book. A book so bound lies perfectly flat on a photocopier's platen without strain . Two page spreads can be photocopied without any depression between the pages. Microfilming and digital scanning gain similar advantages. Second, the drape of a paper, its ability to fall into the gutter, is no longer important. Assuming that edge cockling can be controlled, the grain of the paper is irrelevant. The action of this type of book actually improves with the stiffness of the paper. Loose collections of boxed art plates can be easily consolidated in a adhesive quarter-joint binding with the only intrusion on their original integrity being a line of adhesive equal to the thickness of its bound edge. Heavier card stock and even paperboard materials can be inserted throughout the text without adding any strain to the book when it opens. On particularly thick, heavy books a paperboard insert placed in the middle of the textblock can add additional support to the book as it sits on the shelf. And third (a little more speculative), glossy papers which suffer a high rate of adhesive failure gain in relative strength and achieve a higher rate of survival.

The adhesive quarter-joint binding adopts modern materials and attempts to maximize their advantage. It begins an exploration of which book structures are based on material limitations and which are traditions habitually repeated. Further, it seeks to understand the source of a binding's strength. In this exploration the traditional book becomes the oak tree. We expect it to act like an oak tree. We expect it to feel a certain way in our hands. We expect it to resist movement beyond a given point. When a book acts contrary to our ingrained expectations, we deem it weak and unfit. The appearance of weakness, however, can be another type of strength. The book can become the blade of grass where the ability to yield replaces the ability to resist. For this to happen we must rethink our expectations of how a book should act and renew our understanding of a book's dynamics. The adhesive quarter-joint binding is one step in this direction.

 

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