| Tech Tip |
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| Watch COOL-BIND Temperature |
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| Running COOL-BIND is much like running a conventional 350°F EVA with some important distinctions. |
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| 1. Because COOL-BIND's running temperature is 250°F (121°C), it becomes water thin at 350°F (175°C). This makes mixing with other EVA's difficult. Thus, trials should be conducted starting with an empty pot, and only to 250°F temperature. |
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| 2. Monitoring temperature is important because COOL-BIND operates best in the 250°-275°F (121°-135°C) range. Viscosity is critical to carrying the proper amount on the second wheel and depositing 20 mils (0.51mm) to the backbone. |
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| 3. The spinner temperature should be set about 20°F (-6°C) higher than the pot temperature to achieve a smooth coating and cutoff. |
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| Chipping Out |
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| One of the major problems in book quality is the chipping out of a corner of a book during the trimming process. This problem occurs generally with cover stock that has been UV coated or varnish coated. The following contributes to this problem: |
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| 1. The coating is very brittle. |
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| 2. The cover has been scored deeply, breaking the fibers. |
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| 3. The paper has been dried out, making it brittle. |
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| 4. The hot melt builds up on the knives, which tear the cover on the upstroke. |
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| 5. The coating softens, causing the cover to tear easily. |
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| 6. The angle of the blade is too steep or too shallow |
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| 7. The blades are dull |
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| The binding of the book and the hot melt used can contribute to many of these causes. If the hot melt is too hot and has not set, it will smear onto the knives and eventually build up. Pieces of the clay coating or the paper itself will adhere to this buildup, making the problem worse. Trimming off line generally helps this problem, but is costly and will cause the knives to become dull faster because of the hot melt's hardness. High temperature hot melts also cause the paper to become dry at the point of application, so the paper loses its flexibility at that point. This weakness allows the paper to tear easily, causing the coating to chip out. |
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| By running low temperature hot melts, such as COOL-BIND, the paper does not become brittle, and the hot melt does not build up on the knives. The angle of the cutting edge, however, is very important, and reducing this angle is generally beneficial. |
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