The covers used in surface sizing must be ground frequently and dried
up before putting them back into use as water penetrates into the cover.
Water impairs the bonding of the cover to the metal roll body. The
drying period before re-use should be two thirds of the previous period
of use, however, no less than 4 weeks. The maximum recommended
period of use is 15 weeks, especially if alkyl ketene dimer (AKD) sizing
agents are used in the process.