The Effect of Variables on the Penetration of Starch Applied at the Size Press and the Relationship of Penetration to Strength Properties

A sheet internally sized with rosin was impregnated at the size press with starch under varying conditions of temperature, moisture, and speed. Penetration was studied with a view to final sheet properties. A sliding microtome was used to cross-section the sheets. The sections thus obtained were extracted with hot water and hydrochloric acid. A photocolormetric determination of starch was used utilizing the characteristic starch iodine reaction. Increased temperature increased the pickup and penetration of starch. Increased moisture of the base paper initially aided pickup and penetration. High moisture tended to be retard pickup and penetration. Increasing machine speed increased pickup and penetration. Starch on the surface seemed to improve burst more than an equal amount of starch within the base sheet. The addition of starch greatly reduced tear. The greater the penetration the greater the tear reduction