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Offline Remoist Glue Applications

Until the 1990s, sheet-fed 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 sheet-fed and non-heat-set 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 cause excessive paper curling and cracking.  Second, cold adhesives tend to be thicker right 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 8½” side, an extrusion machine will detect the presence of paper and begin the glue flow ¼” away from the paper edge.  Then, it will apply glue for 8”, stop for ½”, apply glue for another 8” and finally stop the flow ¼” 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 raggedy 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 inline at right angles to each other.

Inline Application
At Rickard Bindery, most of our remoist glue jobs are done inline with other binding processes.  For example, we 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 inline.  Needless to say, inline production greatly reduces turnaround times and cost, making non-heat-set web and sheet-fed companies competitive on many jobs.  Regardless if the piece is a self-mailer, or will be bound into another product, inline production is a good value.  Our company 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 we get a frantic call from a web printer whose remoist glue doesn’t work for some reason.  Recently, we saved a 1,000,000-piece job for a company that ran it off 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.

Layout Considerations
If you have a form with side-by-side envelopes, don’t have the glue strips rest against each other as they’re coming off 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.

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Remoist glue makes many direct mail programs better.  Printed pieces with easy ways to respond are more effective than those without.  The bottom line is that remoist glue makes response mechanisms easy and quick to use.

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