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May 1, 2001 12:00 AM
Although many different types of adhesives are available, EVA-based hot melts, such as those offered by National Starch and Chemical and H.B. Fuller are the most common. Many hardcover and layflat books are bound with water-based poly vinyl acetate (PVA) adhesives. Difficult-to-bind papers, such as glossy stocks with ink bleeding into the gutter (annual reports), are bound with polyurethane reactive (PUR) glue to prevent ink solvent migration. Phone books must be bound with protein (animal) glue or with a more expensive, recyclable hot melt to comply with environmental restrictions.
Binders may mix some of these adhesives when using a “two-shot” application system, i.e., a primer adhesive. For example, the binder might use a PVA primer and a hot melt; or, two different hot melts, one with low viscosity and another with a high viscosity to assure a rigid backbone.
Choice of adhesive is also influenced by spine preparation techniques. This decision is made more complex by several factors — thousands of different papers and coatings, grain directions, inserts, etc.
One cautionary note: It isn't at all unusual for crews to take it upon themselves to change the temperature of a hot-melt adhesive. I know of one instance in which a crew, reasoning that they could do a better job than the previous shift, changed the temperature by more than 40 degrees! Such adjustments can play havoc with the viscosity and subsequent binding quality, which is why most modern tools are digitally controlled.