Rewet in wet pressing of paper

Abstract

Wet pressing in papermaking removes water by pressure applied over time, but some of the expelled water may return to the web in an action called “rewet.” This water, and the other remaining water, must be removed by drying. To understand the underlying factors of rewet, we have developed a mathematical model of it comprised of a time-dependent term that accounts for water flow from the felt to paper and a time-independent term that accounts for splitting of interfacial water between the felt and paper. Our model is consistent with measurements from the literature and can be used to understand how paper properties, press operation, and felt design can minimize rewet.