Environmental Condition
Environmental condition describes a state where the moisture content of the air remains at a fixed percentage without fluctuation. For the testing of paper and board, static relative humidity is maintained in controlled laboratories to ensure that all samples reach a consistent equilibrium moisture content. Standard conditions are typically set at fifty percent humidity and twenty three degrees Celsius.
This stability is necessary for the repeatable measurement of properties like stiffness, curl, smoothness and tensile strength.
Conditioning Process
Paper is a hygroscopic material that gains or loses water based on the surrounding atmosphere. By placing samples in a room with static relative humidity, the fibers are allowed to expand or contract until they reach a steady state. This process eliminates the influence of previous storage history and ensures that the physical test results are comparable between different laboratories.
The time required for conditioning varies with the thickness and density of the board, as thick grades take longer to reach the interior of the sheet.
Accuracy Requirement
Accuracy requirement demands that even small changes in the air moisture are prevented because they lead to noticeable variations in the test data. Maintaining a constant level prevents the curling and dimensional changes that occur when the web is exposed to cycling conditions.
