Moisture Regain between Mill Conditioning and an Unheated Warehouse
Unheated storage drives moisture ingress along sheet edges via psychrometric gradients, requiring sealed barrier wraps and strict thermal acclimation before press run.
Stack Thermal Mass
Heat Capacity
Storage properties of paper determine how slowly a large mass of material reacts to environmental shifts. The stack thermal mass of a full pallet means that the core of the load can remain cold even after the exterior has warmed. This property is a result of the density and specific heat of the cellulose fibres combined with the air trapped between the sheets.
Temperature Lag
Differences between the paper and the pressroom environment create a risk of condensation. When cold paper is exposed to warm, moist air, the water vapour turns into liquid on the edges of the sheets. Such moisture absorption causes the paper to swell and creates wavy edges that interfere with the printing process.
Acclimatisation Protocol
Pallets must remain wrapped in protective film until the internal temperature matches the ambient air. Most printers use a probe to verify the core conditions before starting a production run. If the material is too cold, the ink may not set correctly and the sheets could stick together in the delivery pile.
Sufficient time in the warehouse is necessary to reach equilibrium and ensure the stability of the substrate. Proper management of the storage climate prevents many of the defects associated with temperature shock.