The term insidious refers to something harmful that sneaks up on us, seemingly out of nowhere. I can think of nothing more daunting in our business than to have the unexpected occur…especially when it spells disaster on the job. In this article, I will discuss one such frightening phenomenon—insidious inks.

While the actual chemical account of insidious ink (or insidious solvent) occurrences is complex, the basic problem is simple. Occasionally, when the variables are just right (or should I say wrong), ink solvents make their way into the spine of a book and attack and break down the adhesives in the bind causing the pages to fall out. When this happens, make no mistake, the entire job is destroyed and there is no quick fix. The only options are reprinting both the covers and the first and last leaves of text, rebinding, and retrimming (making the book 1/8" shorter in each direction)—or, worse yet (and what recently happened to us)—running an entire reprint.

Peter Pape, President of The Riverside Group, and a good friend and colleague of mine, described this phenomenon. “Insidious ink issues are curious because while every corner of the industry is well aware of them—be it printers, binders, glue, ink, or paper manufacturers—the subject is taboo and no one is willing to take the blame for this problem. It’s as if no one wants to admit it actually exists. I suppose this is true because on the rare occasion when this problem does occur it is difficult to predict, the results are disastrous, and there is no quick solution.”

Because there is little documentation on this subject, I talked to a few people who may be able to shed some light on it. Chuck Cline, Technical Services Manager for the book binding division of National Starch and Chemical Company, an adhesive supplier based out of Bridgewater, New Jersey, described the problem. “Insidious ink solvents are usually found in highly coated or glossy nonporous stock with heavy ink coverage that bleeds into the spine. Heavily varnished paper provides a poor surface for any type of adhesive because the glue has difficulty penetrating the paper and has little to grab on to. This, coupled with the fact that the ink is floating on top of the paper because it cannot penetrate the fibers, causes difficulties.”

Two ink vehicles are usually to blame: white mineral spirits (a paint thinner) and magee oil. Interestingly, several people have told me the solvents have a distinct odor. When ink solvents have migrated into the spine, all you need to do is open it (anywhere from an hour or two after binding it up to a few weeks later) and you can actually smell the problem right away. At one renowned research institute, FOGRA in West Germany, researchers found that half of all the solvents used on sheet-fed offset lithography were still not dry three months after the jobs were printed!

Another frustrating aspect of this problem is that initial page pull and flex tests can yield great results misleading everyone to believe that all is well. Page pull tests measure the pounds of pressure a page can withstand before it is either torn or pulled from the binding. The equipment mechanically grasps a page and pulls, gradually applying more and more pressure. Flex tests simulate a person turning a page back and forth by mechanically pulling a book leaf in 120° arcs. It measures the number of turns a page will withstand before breaking from the spine.

Al Zuccarello, Senior Territory Manager, Graphic Arts Division, for H.B. Fuller, an adhesive supplier based out of St. Paul, Minnesota, explained, “Insidious inks can be so slick and so dense that the glue cannot penetrate to the paper fibers. In many cases, the adhesive is bonded to ink on the surface that may be anchored to nothing. Typically, this difficulty occurs in jobs that are dried by heat offset. Other problems occur when the ink is dried too quickly or in an improper manner and has not locked itself into the paper fibers. High boiling solvents and oils from the ink can migrate into the hot melt on the spine of the book and change the properties of the adhesive. Ink solvents, when absorbed into the glue, can also interact with the tackifiers found in adhesives and make them tacky, like a pressure-sensitive hot melt. Sometimes this results in poor cover adhesion. Whatever the cause, solvent entrapment attacks the structural integrity of the adhesive.”

So, now that we are in basic agreement about the cause of insidious ink, how do we prevent it? Here is a compilation of tips offered by those who have dealt with this problem:

First and foremost, plan ahead. If you are planning a job that is full-color, requires heavy ink coverage (especially ink that bleeds into the gutter), or is on a coated or varnished stock, contact your finisher before the job is run. They can offer advice on many issues including how much to strip out to accommodate a bleed and recommended paper stock. They can also test the adhesion by wrapping a sample airtight for at least two weeks in an impervious material.
Avoid printing cross-grain. Printing cross-grain on an adhesive-bound book, especially on heavy, glossy coated papers, spells trouble.
Use PUR adhesives. PUR (polyurethane reactive) glues have proven to be unaffected by ink solvents and therefore are an excellent choice when insidious ink may be a problem. PUR glues also provide flexibility, durability, and layflat qualities. In doing so, however, be sure your finisher is experienced at working with PUR adhesives.
Sew the signatures. When the properties of a book lend themselves to insidious ink problems, consider sewing the job for extra strength.
Allow ink to dry properly. The incredible push for speed in the printing industry is probably the single biggest culprit when it comes to insidious ink problems. Newer inks that are designed for rapid initial setting contain solvents to promote the drying process. Ironically, it is these very solvents that can cause the problem with insidious inks. Additionally, the pages are simply not cured long enough before they are passed on to the finisher. Once the pages are stacked on top of one another, the solvents become trapped.
In the words of Werner Rebsamen, Professor in the School of Printing at the Rochester Institute of Technology, trade consultant to the binding industry, and an expert on this subject, “Unfortunately, no one wants to acknowledge that insidious ink problems exist. The truth is, there are, and have been, multimillion dollar lawsuits filed over this very issue. A risk none of us should be willing to take.”