Atmospheric Standard
Standardized environmental preparation of cellulose-based materials ensures that physical strength tests are comparable across different laboratories and production runs. Adherence to iso 187 board conditioning requires exposing paper samples to a controlled atmosphere of twenty-three degrees Celsius and fifty percent relative humidity. This process ensures that the moisture content of the board reaches a stable equilibrium state before any physical testing begins.
Because the mechanical properties of paper fibers are highly sensitive to moisture, uncontrolled testing environments lead to highly variable and inaccurate results.
Moisture Equilibrium
Moisture acts as a natural plasticizer within the cellulose matrix of the paperboard. When humidity rises, the fibers expand and soften, which decreases tensile strength while increasing stretch. Conversely, dry conditions make the board brittle and stiff, which artificially inflates edge crush test values.
Reaching a true equilibrium requires the board to be suspended individually in the conditioning room to allow free air circulation around all surfaces of each sample sheet. Thick boards and dense linerboards can require more than twenty-four hours to reach this stable state.
Physical Testing
Formal quality audits and commercial disputes require standardized conditioning as a prerequisite. Without this step, structural measurements are technically invalid. Controlled atmosphere chambers are therefore standard installations in paper mills.
