"Thread Sealing Aids in Perfect Binding Process"

[Column #38, 2/98]

In past articles, I've discussed PUR (polyurethane reactive) glues and layflat binding at length. Now that we are in the middle of annual report season, the need for advanced adhesives has never been more evident. The demand for perfect bound books continues to grow as runs get shorter, budgets get tighter, and the necessity for perfect bound books with more lasting power becomes imminent. While we certainly can't complain about the growing demand for this service, it has driven continuous improvement in the perfect binding arena, which also means more investment on my part (and my customers')!

Most people in the printing industry understand the shortcomings of traditional perfect bound books-primarily their lack of strength and durability over time. Unlike sewn books where each signature is attached to the others, the pages of a perfect bound book are merely roughened at the backbone and glued to the cover using a hot-melt glue. For a book that will be subject to heavy use, the loss of page strength can be critical. In addition, perfect bound books are notorious for not laying flat. This is particularly troublesome when we're working with heavy coated stock against the grain.

To overcome these problems, PUR glue and layflat (Otabind®) technology have become increasingly popular in the United States. PUR glue provides great page strength and layflat properties. It also overcomes many of the inherent problems with hot-melt glues (i.e., proper glue drying, temperature conditions where the books are both stored and used); however, it can be cost-prohibitive to use PUR adhesives in mass-marketed perfect bound books. Otabind® technology allows a book to lay flat when opened to any page. As a result, both of these advancements have become commonplace for heavily used books that require hands-free reading such as software manuals, cookbooks, and travel guides. Otabind® is a cost-effective alternative to mechanical binding and is especially handy when used in combination with PUR adhesives.

I am painfully aware that all of this great technology still isn't enough. Annual report season is noted for books with fancy tight cross-page alignments that customers want to open flat-with no glue seepage. Often, printers don't realize that anytime a book is done with coated stock and heavy ink coverage (which is often the case in annual reports), the glue will repel slightly. We also need to ensure there is enough glue to prevent the pages from falling out. Striking the right balance between the amount of glue necessary to hold the book together and minimum glue seepage is always a battle. When a job requires aggressive roughing to provide enough paper fiber for the glue to grab (heavy coated stock against the grain with a lot of ink), the final product can look shoddy because the pages acquire a sawtooth-like appearance.

Recently, a customer with a book that was printed on heavy coated stock against the grain (the worst conditions for perfect binding) asked us to guarantee that the book would lay flat, the pages would not fall out, and there would be no glue seepage or rough edges-piece of cake, right? Our response: Have the book Smyth sewn. It is more expensive and time-consuming but will ensure the product will have all of the desired properties. This, of course, was not welcome news for a customer on a tight budget and a tight schedule.

One cost-effective solution to this problem is a technology known as thread sealing. It has been around for years in Europe, Asia, and Australia but is extremely uncommon in the United States. However, it is now available here through a couple of the folder companies. Thread sealing was first introduced in the United States at Graph Expo '95 and again at the Heidelberg's exhibit at Print '97. There are currently two machines available here, the Stahl FS 100 Thread Sealer and the MBO SF 56 Thread-Sealing-Folder. These machines offer attachments for folders that sew the spine of each signature with a plastic-coated thread during the folding process (each signature is sewn to itself and is not attached to the remaining signatures). The threads are then heat-sealed to keep them in place and the individual signatures are fed out of pockets in the normal perfect binding process. They do not go through a grinding procedure (thus avoiding jagged edges) and the cover is attached. The system works with a variety of paper grains and folders and provides an affordable way to increase the strength of a perfect bound book and provide layflat qualities with no glue seepage. Thread sealing offers about 70 percent of the strength found in a sewn book and more than twice the strength of a traditional perfect bound book. It is also advantageous because it eliminates an entire process necessary for Smyth sewing. When a book is sewn, loose signatures must be gathered, then sewn on a sewing machine, then taken, in the form of a book block, and placed back in the binder to glue the cover around the back of the book.

Although thread sealing has been around in Europe for many years, the newer, more advanced machines have overcome many problems that existed with the older equipment. Today's technology offers digitally controlled electronic makereadies that are much quicker and more accurate to set up, increased speeds of up to 6,200 16-page signatures per hour (based on 23" x 35" sheets), and portability.

It's strange how solving one problem often leads to more, creating an endless cycle where no one is ever completely satisfied. It was just a couple of years ago that the only glues available were hot glues and the books didn't open up. Now that they can open up, we're saddled with glue seepage and rough edges. So then, we find ourselves back at square one with books that need to be sewn and customers who don't want to spend the time or money to do so. Now here we sit waiting to see if our customers will pay the extra money for thread sealing. The machine costs anywhere from $120,000 to $200,000-and that's for each folder using this attachment! I have a feeling it won't be long before designers will discover this technique and I'll have to get my checkbook out, again.

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