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D.H. Everett, J.M. Haynes and R.J.L. Miller. Kinetics of capillary imbibition by fibrous materials. In Fibre-Water Interactions in Paper-Making, Trans. of the VIth Fund. Res. Symp. Oxford, 1977, (Fundamental Research Committee, ed.), pp 519–534, FRC, Manchester, 2018.


A simple gravimetric technique for determination of the rate of capillary imbibition of wetting liquids by porous solids is described, and illustrated with results obtained with a wide variety of liquids on a range of glass-fibre filter papers.

Application of the familiar Washburn equation to the results yields an ‘imbibition equivalent’ pore size. Although, in the case of fibrous materials, it may be difficult to relate this to any real geometrical property, it nevertheless provides a practically useful description of the materials’ behaviour. The effects of prewetting on subsequent imbibition are explored.

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