Retention of Pigments and Cellulose Fines

Only particles larger than the openings in the paper web and the papermaker s wire can be entrapped mechanically. Kaolin particles, for example, have a hydrodynamic 

Cationic starch is a frequently-utilized retention aid, especially when paper strength improvement is a second objective.141,142 Low pH activates tertiary amino starch, but at pH 6 an amphoteric starch, and at pH above 7 a quartenary ammonium starch, will be needed. 

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