The effects of preconditioning, moisture content and relative humidity during adsorption and desorption on the compression strength of paper were evaluated for a kraft liner and an NSSC-fluting over a range of moisture content from 1-23%. The method used was the STFI Short Span test.
In general, the results show that compression strength decreases with increasing moisture content. More specifically, if compression strength is evaluated as a function of moisture content, the data points fall on a single curve for both adsorption and desorption . This result is independent of the moisture history of preconditioning of the sample.
If compression strength is evaluated as a function of the relative humidity of the test environment, the moisture history and preconditioning both exert a large influence on the test result. This indicates that samples of unknown moisture history should be preconditioned in much drier atmospheres than previously recommended.