Abstract
What Parker Print-Surf (PPS) roughness means was discussed by comparing the theoretical equation to that of Bekk smoothness and by determining the wavelength range which PPS represents by the spectral analysis applied to the stylus profiles of paper. As a model of air flow through channels between paper surface and the metal measuring head of an air-leak type smoothness tester, the PPS model is more comprehensible than the Oken type (Bekk) model. However, what the testers survey is fundamentally common to the two methods. Thus, the two equations standing for the models are convertible and the conversion equation was led to be G3=18.65_??_, where G3 is PPS roughness; TB Oken type smoothess. The empirical data exhibited that the conversion equation applies to many papers except those with different compressibility. The correlation between PPS roughness and centerline average (Ra) at several cut-off wavelengths calculated from stylus surface profiles showed that PPS tester presses out paper surface so that the surface shape agrees with roughness at a cut-off wavelength of 234μm for calendered handsheets. This cut-off wavelength gave the least sum of squared deviations from the theoretical conversion equation, G3=2.13×Ra. Oken type smoothness was considered to survey the longer wavelength components than PPS roughness. However, the best-fitting cut-off wavelength was greatly dependent on the surface deformability of paper at a testing pressure in view of papermaking history and converting processes.
