Unheated Warehouse Storage Impact on Multi Ply Boxboard Moisture Equilibrium
Unheated storage alters multi-ply boxboard moisture equilibrium, swelling sheet edges, reducing internal bond strength, and causing severe converting curl.
Thermal Acclimatization Protocol
Environmental Standard
Systematic procedure for bringing palletized paper goods to the temperature of the processing facility prevents the formation of condensation on the surface of the sheets. Thermal acclimatization protocol specifies the duration a shipment must remain sealed in its original protective wrapping based on the temperature difference between the transport vehicle and the warehouse. Climate control is necessary because cold paper introduced to a warm, humid room acts as a condenser, drawing moisture from the air directly into the fibers.
The resulting swelling leads to dimensional changes that make accurate printing and registration impossible.
Tables Provided
Tables provided by paper manufacturers indicate the required hours of rest for different volumes of paper, with a full pallet often needing forty-eight hours or more to reach equilibrium. Technicians use infrared thermometers to check the temperature of the stack before removing the outer moisture barrier. If the wrapping is removed too early, the edges of the stack will expand faster than the center, creating tight edges.
Large temperature swings during winter months require longer waiting periods compared to the milder shifts seen in the spring. The protocol applies to all grades of paper but is especially important for high-quality coated stocks used in multi-color offset lithography.
Adherence to Guidelines
Adherence to guidelines reduces the risk of press jams and ink drying problems. Consistent temperature throughout the stack ensures that the chemistry of the fountain solution and the ink remains stable. Stable environmental conditions are the foundation of predictable print results.