A pilot paper machine evaluation of the effects of pressing on newsprint quality

The effect of forming and pressing was investigated on a pilot paper machine equipped with two different wet-ends and a press section with four nips. The design of the former has the greatest effect on sheet structure, strength, surface properties, and print density index. Increasing the loading of either the first or fourth press up to a critical value increases the strength of newsprint. Strength will decrease if the loading is increased beyond this critical value. The print density index of the sheet is directly related to the consolidation of the sheet in the press section and calender.