Development of the Metering Size Press: A Historical Perspective, 2000 Metered Size Press Forum
The conventional two-roll pond size press has been standard component of paper machines for nearly a century. It has been used not only for starch surface sizing but also for pigmented precoating and coating. It suffers a number of limitations. Pickup is dependent on internal sizing level and moisture content of the sheet, necessitating overdrying the sheet in the main dryer section to flatten the profile entering the size press. It saturates the sheet and has poor runnability on lightweight and other low wet tensile strength sheets. When used for pigmented coatings, it requires high binder levels. It has speed limitations due to the hydodynamics of the pond. As machine speeds increased, size press designers tried to the use of larger rolls, but the practical spped limit was about 800 m/min.