The Root of the Problem

When a water-based coating hasn't been fully dried, sheets block in the load, Duncan said. And if a UV coating isn't agitated during printing, wax can be distributed unevenly also causing blocking.

Ambient conditions can also have an effect on coatings when using a thermal dryer on water-based coatings, said Stephen Lapin, vice president, technical director of Northwest Coatings. "It will be more difficult to dry the coating on a humid summer day compared to a dry winter day," he said. "Air movement in the dryer is very important for drying water-based coatings and is much more effective than IR heaters with little air movement. Adding more heat to the substrate is not always a good thing, and can actually make blocking worse if the heat remains upon rewinding or stacking of the material after drying."