| Cline's Comments |
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| Best Methods of Drying the Adhesive when Gluing off |
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| The gluing off operation in edition binding is a critical step in making a quality book. Most books are glued off with a liquid resin, either as one coating, or in combination with a hot melt as a two-shot operation. In either case, the liquid adhesive must be dried properly before subsequent operations. |
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| The gluing-off resin must be a relatively low viscosity product to coat the backbone properly and penetrate into the fibers of the pages. If the book is Smythe sewn, enough adhesive must penetrate between the signatures to hold them in place. Burst bound signatures require low viscosity to adhere the innermost pages of the signature. Coated pages will hinder the glue's drying ability, since the glue has difficulty absorbing into the paper. In binding a 24 or 32 page signature, drying the adhesive becomes even more difficult because of the larger area. |
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| Drying Methods |
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| The two most common methods for drying adhesives in the U.S. are infrared heaters and gas-open flame heaters. Europe and Canada turn to radio frequency drying. |
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| Regardless of the drying method for the gluing-off resin, the key is to apply the least amount of heat to achieve the desired result. In some cases, especially when using an absorbent paper, one or more sets of heaters can be turned off to still obtain a dry backbone. It is best to turn off the heater closest to the glue pot so the adhesive can start penetrating the paper before the heat starts forming a film. When you've applied the right amount of heat for drying, the backbone should be dry to the touch after exiting the gluing-off machine. The bookblock itself should be no more than slightly warm. |
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| Problems |
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| Excessive heat will cause the following problems: |
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- If books are stacked off prior to trimming, they will tend to pressure block.
- If the books are sent in line to the trimmer and trimmed two up, they will pressure block.
- If a hot melt is applied before trimming, it will not set up, causing smearing when trimmed.
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| Insufficient heat will cause the following problems: |
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- Adhesive builds up on the belts following the gluing off machine.
- Excessive adhesive squeezes between pages.
- Poor adhesion to the lining hot melt.
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| Different methods of gluing off as well as their advantages and disadvantages are discussed in the lead article of this newsletter. |
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Chuck Cline |
| Technical Service Manager - Bookbinding |
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