On the paper machine, the size press is used to apply surface size to dried paper.182,183 Starch is the most frequently used binder in surface sizing. fluting corrugated paper machine speeds; wet-end sizing of the sheet; and water content of the sheet.
High liquid viscosity, large roll diameter, soft roll covers and high newspaper machine speed increase starch transfer, while high nip pressure counteracts these drivers. Starch cationization has no affect on pressure-driven penetration, provided the hydrostatic pressure is high and the viscosity of the dispersion is low.
The same basic test liner paper machine used to produce writing and printing paper are also used to form paperboard. Although starch is usually added at the wet end of the coated board duplex paper machine as a liquid feed directly to the furnish, other systems which place the starch directly on the formed sheet while it is still on the wire of the Fourdrinier machine or on the felt of the cylinder machine may be used.