In this study fiber cell wall porosity was altered by fiber line simulation in a laboratory. The changes in the fiber cell porosity were analyzed with a water retention value (WRV) test. Pore size distributions were measured by differential scanning calorimetry (DCS), and atomic force microscopy (AFM) was used to determine the cell wall pore area from cross sections of the S2 layer of the cell wall. WRV was shown to correlate with the amount of water in the pores with a diameter of at least 200 nm. Changes in the non-freezing and total bound water did not affect the WRV. The calculated shrinkage forces generated by the capillary forces in different pore cell wall structures correlated with the sheet densities generated by fiber networks. It was observed that the swelling of the cell wall, defined as an increase in the diameter of the cell wall, was most likely not occurring or was very difficult to detect.

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Comparison of industrial and laboratory pulps from Pinus radiata showed higher energy requirement and lower tear index at the same tensile strength in the case of industrial pulps. Chemical differences between pulps were negligible and cannot explain the strength differences observed. Morphology of the fibers changed during processing with an increase in kinks and curls for industrial pulps. Increased twists and wrinkling in mill fibers were observed based on scanning electron microscopy images. Results from water retention value and fiber saturation point measurements showed reduced water holding ability of industrial fibers. Simons' stain and hydrogen nuclear magnetic resonance confirmed a higher proportion of macropores in the fibers of industrial compared to laboratory pulps. Evidence supports the presence of both micropore closure and creation of new mesopores and macropores during industrial processing. A combination of fiber damages, porosity changes, and induced deformations seems to play the main role in the lower strength properties of industrial pulps when compared to laboratory pulps.

The SuperBatch™(SB), CompactCooking™(CC), and Lo-Solids™ (LS) modified cooking methods were evaluated relative to the cell wall surface and paper technical properties of bleached Eucalyptus globulus and Eucalyptus nitens. E. globulus pulps presented higher screened yield and brightness than E. nitens, which needed higher H-factor to reach a kappa number target. Independently of the cooking method or species, all the samples consumed similar amounts of ClO2 to reach a brightness of 90% ISO. E. nitens pulps showed lower carbohydrates and higher extractives content on the fiber surface, regardless of the cooking method. E. nitens presented slightly higher surface charge of the bleached pulps. Surface charges of CC and LS pulps were higher independently of cooked Eucalyptus species. Water retention value (WRV) for E. nitens pulps were higher than for E. globulus. No differences were observed in refinability of different cooking methods, however E. nitens pulps showed higher tensile and lower bulk compared to E. globulus. E nitens presented a thinner fiber cell wall than E. globulus. This seems to be more relevant for paper technical properties and WRV than fiber charge or surface composition. No correlation between surface composition, fiber surface properties, and paper technical properties among the cooking methods could be determined.

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