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What causes case board warp?

Posted on March 08, 2016 by Maria Verros, Online Marketing Manager
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If you are in the book binding business, case board warp is something you are probably familiar with. In fact, if  you work with case board at all you may have experienced warp issues at some point. We recently visited with a case-making customer that was experiencing case board warp. Like many who have been in a similar situation, this customer looked to their board and glue suppliers as resources for understanding why case board warps.

What is case board warp?

Case board warp happens when the board becomes bent, curled or distorted in some way. Most times board warp can be attributed to moisture. In case-making, case board warp can make the substrates difficult to work with. Many case-makers have issues with board warp in the winter months when there is very low humidity outside making the environment very dry. Once the board is exposed to humidity or the lack of, such as in a manufacturing environment, it may begin to warp.

Board Warp
Notice how this board is not laying flat - this board has been exposed to moisture and is warped.
 
The Science Behind Board Warp

All case board is made from recycled fibers which has sometimes been recycled up to 15 times. Each time the board is recycled, the fibers become shorter and shorter which causes it to react more dramatically to moisture.

Ways to Limit Board Warp
  • The percentage of moisture in the board fibers is delivered at a specified range. Since the environment will affect the reaction of moisture loss or absorption it is important to have a controlled humidity in your manufacturing facility if possible.
  • Another culprit for case board warp is the amount of moisture in the glue. The amount of glue applied to the board will affect the the likelihood of warping. More glue results in more moisture which results in more warping because the porous board will absorb the water. You want to use the least amount of glue possible to achieve your desired adhesion. You can usually achieve this by using a high quality glue which requires a thinner application.
  • The grain direction of the case board is another detail to pay close attention to. The grain direction is the direction that most fibers are oriented. The recommended grain alignment in case-making is parallel to the book spine. Aligning the grains this way will help to limit potential for warp.

We hope this helped answer your questions regarding case board warp. If you have any additional questions, feel free to reach out to our technical team.

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Thanks to our friends at Eska Graphic Board for their help on this post.

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