Board stock-warping problems are more prevalent in the spring and fall of the year and are generally due to moisture imbalance of the board or the adhesives, which causes fibers in the board to swell or expand.
How to Avoid Board Stock Warping?
1- Test the grain direction on the case board
It should flex parallel to the spine of the book.
If it flexes perpendicular to the spine of the book it is cross-grain.
Which will tend to cause more warping during case-making.
2- Allow the Board To Come To Moister EQUILIBRIUM
The board may arrive at its destination at a lower level of moister connect that it will normally be subjected to during the case-making operation. Allowing the board to come to EQUILIBRIUM in the case-making environment will minimize its chance of warping due to moisture in the case-making adhesive.
3-Use a Winter Grade Animal Glue
There is summer grade and winter grade for most animal glues. During the summer, when the humidity is high, animal glue needs to dry quicker. During the winter, when the air is dry, certain materials need to be added to the animal glue to allow for slower drying. Be sure to use summer grade during the summer and winter grade during the winter.
4-Do not add water to the casing-in product
Most casing-in glues are supplied ready for use. If the adhesive is specifically for casing-in, it will contain materials that will minimize the chance of warping. Adding water to these products will increase the chance of warping.
It should flex parallel to the spine of the book. If it flexes perpendicular to the spine of the book it is cross grain. Which will tend to cause more warping during case-making.