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The quantitative microscopic analysis of paper cross-sections : sample preparation effects

A quantitative technique is being developed for the analysis of paper cross-sections. This technique provides a Z-directional profile of the sheet and measures of wall area, total pore area, interfibre pore area and lumen area. The intention is to be able to relate pulp processing conditions to sheet structure and end-use performance. With this technique paper samples are embedded in resin, cross-sections are then exposed by abrading and imaged by confocal laser scanning microscopy. The present paper investigates the effect of sample preparation on these parameters by subjecting uncalendered and calendered sheets to a number of embedding and sectioning procedures. The cross-sectional thickness of uncalendered sheets deviated from standard thickness by approximately 1 to 5%, whereas for calendered sheets, cross-sectional thickness showed a 20 to 30% increase over standard thickness. There was no evidence of fibre swelling or shrinkage resulting from the embedding process; instead the increased cross-sectional thickness of calendered samples is attributed to fibre rising.