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R.W. Hoyland, P. Howarth and R. Field. Fundamental parameters relating to performance of paper as a base for aqueous coatings. In The Fundamental Properties of Paper Related to its Uses, Trans. of the Vth Fund. Res. Symp. Cambridge, 1973, (F. Bolam, ed.), pp 464–491, FRC, Manchester, 2018.


In relating the quality of the coated sheet to the properties of the base paper, the  liquid absorbency of the base paper is a most important consideration for all coating processes.

Nor surprisingly, base sheet absorbency has received a great deal of published attention. Recently, there has been a growing appreciation that the Lucas-Washburn equation does not fully explain the penetration of aqueous fluids into paper. The shortcomings of the Lucas-Washburn equation are clearly indicated in the work described on the mechanism of the size press.

A new method of following the penetration of aqueous solutions and suspensions is presented.

Analysis of the results indicates that a wetting time exists and that the Lucas-Washburn equation is inadequate to describe the penetration of aqueous fluids into paper.

A new model for penetration is suggested, which allows for the swelling of the sheet that occurs as penetration takes place. A penetration equation is derived from this model.

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