Moisture Balance
Attainment of a stable state where a fibrous material neither gains nor loses moisture when exposed to a specific ambient atmosphere defines the physical limit of fiber-water interaction. This state of hygroscopic equilibrium is reached when the partial pressure of water vapor within the paper sheet equals that of the surrounding air. The relative humidity of the environment determines the final moisture content of the substrate at this point.
Ambient Interaction
Paper behaves as a hydrophilic material that continually exchanges water molecules with the air until the vapor pressures are balanced. If the surrounding air becomes drier, the sheet loses moisture and shrinks, which can cause paper curl or edge waves. In contrast, exposure to high relative humidity causes the paper to absorb water and expand.
These dimensional changes can disrupt the registry of multi-color printing runs or lead to feeding jams in high-speed converting machinery. Stabilizing the storage hall at a standard climate of twenty-three degrees Celsius and fifty percent relative humidity ensures that paper remains stable and flat throughout the production process.
Structural Stabilization
Storing wrapped pallets of paper in the press room for several days allows the sheets to adapt to the ambient environment. This conditioning minimizes the risk of dimensional changes during subsequent print runs.
