Abstract
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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