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Gluing--Sticking With Direct Mail

March 1999

Until the 1990s, sheetfed printers had little opportunity to sell products with remoist glue. Today, short run remoist glue jobs are practical because the current crop of machines yield high quality jobs at good production rates. Both sheetfed and non-heatset web printers now can produce products with direct response reply devices and participate in profitable direct mail campaigns.

There are primarily two ways of applying remoist glue. The older technology—cold application of water-soluble remoist glue—works by transferring glue to paper by either a wheel or a blanket. This process has two main advantages.

First, heat by itself doesn't activate it, which means it's downstream laser compatible. Second, glue application "pads" can be different sizes and run in different directions, which allows the efficient manufacturing of products such as three-sided "U" bar reply devices and stamps.

Unfortunately, there are some significant drawbacks with cold applied glue. First, it has to be run through hot dryers, which frequently causes excessive paper curling and cracking. Second, cold adhesives tend to be thicker at the beginning of the glue strip. Sometimes this thick buildup takes longer to dry and forces operators to choose between having either brittle paper or semi-wet remoist glue that may stick to neighboring sheets. And third, a potential fire hazard is created when conveyors stop running, if there is any paper in the oven.

Extruded Glue
Hot melt extrusion is the other way to apply remoist glue. These machines give operators more control over the placement and appearance of glue strips as they're being applied to the paper. Computer-controlled solenoids allow operators to precisely start and stop glue flow wherever necessary.

For example, if a two-up piece is being glued on an 81⁄2˝ side, an extrusion machine will detect the presence of paper and begin the glue flow 1⁄4˝ away from the paper edge. Then, it will apply glue for 8˝, stop for 1⁄2˝, apply glue for another 8˝ and finally stop the flow 1⁄4˝ away from the trailing edge.

Water-soluble glue applied on a pattern gluer can do this, too, but since pattern gluers rely on timed entry rather than motion sensors, its application isn't as precise. In addition, extrusion hot melt glues rarely curl paper and generally have a professional appearance, while cold-applied glue looks duller, may have ragged edges and tends to curl, since moisture is being added to only one side of the sheet.

A potential drawback of extrusion machines is that they can only apply remoist glue in parallel lines. This means that glue laid down in the shape of a "U" either needs two passes or two machines running in-line at right angles to each other.

In-line Application
At Rickard Bindery, most of the remoist glue jobs are done in-line with other binding processes. For example, operators may apply remoist glue, stop-perforate the sheet, apply seam glue to form a pocket, fold it (barrel folds, accordions and gatefolds), apply wafer seals, slit it and keep the job in mail-sort order—all in-line.

Needless to say, in-line production greatly reduces turnaround times and cost, making non-heatset web and sheetfed companies competitive on many jobs. Regardless if the piece is a self-mailer, or will be bound into another product, in-line production is a good value.

Rickard Bindery, for example, frequently does remoist jobs ranging in quantity from 5,000 to 200,000 pieces, or even more.

Extrusion remoist glue jobs can be fed from cut sheets, fan packs or rolls. Occasionally, a call comes in from a frantic web printer whose remoist glue doesn't work for some reason. Recently, Rickard saved a 1-million-piece job for a company that ran the job without noticing that the glue strip was missing.

The Key Factors
The five key factors of successful remoist glue application are: paper, glue, ink, coatings and atmospheric conditions. Let's take these one at a time:

  • Paper. Knowing the characteristics of the paper is important. Remoist glue rests on the surface of enamel stock, yet is able to create a good bond when moisture-activated. Uncoated stock also generally works fine, but will normally require a heavier line of glue, since it is more porous and some will seep into the sheet.

  • Glue. Understanding the difference between water-soluble and hot melt glue is important. Ask the bindery which glue it intends on using for the project and why.

  • Ink. Generally, remoist glue can be applied over ink with fine results, but problems may occur when activated glue needs to adhere to paper with 100 percent ink coverage. Be safe and plan the artwork so that remoist glue doesn't require adhesion to heavy ink solids.

  • Coatings. Remoist glue doesn't adhere to paper coatings such as varnish. If flood varnishing is planned for a sheet, change the design to spot and knock out varnish from where the remoist strip is to be applied and adhered.

  • Atmospheric conditions. In high humidity areas, it's essential to apply water-soluble remoist glue in a climate-controlled environment. Regardless of glue type, be safe and include a moisture-absorbing packet in each box. These packets draw moisture out of contained areas and prevent remoist glue from unintentionally bonding.

Even perfectly manufactured remoist glue products sometimes will unintentionally bond inside a hot truck, so all preventative measures should be taken.

Layout Considerations
If a form with side-by-side envelopes is being used, don't have the glue strips rest against each other as they're coming off the machines. Unintentional adhesion can occur when glue strips are directly in contact with each other face to face, especially during shipping. Staggering designs so that glue strips avoid contact with each other is a much better way to plan a job.

Avoid flatbed trimming after remoist glue application because it may cause a series of three problems.

First, productivity will decline because sheets will have to be cut in very small lifts in order to clamp properly and not tear, due to inadequate clamp pressure. Second, glue bulk will raise a bump in each lift, resulting in the top sheets being longer than the bottom ones after trimming. Third, cutting through remoist glue wreaks havoc on knives, especially those super-hardened for long life.

Remoist glue makes many direct mail programs better. Printed pieces, which incorporate easy response mechanisms, are more effective than those without.

The bottom line is that remoist glue makes these response mechanisms easy and quick to use.

About the Author
Jack Rickard is president of Rickard Bindery, president of the Printing Industries of Illinois and Indiana, and a former president of the Binding Industries of America. Rickard Bindery specializes in discovering solutions to challenging bindery jobs. He can be reached at (800) 747-1389.


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