Gluing — Sticking With Direct Mail
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.
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.