In general, beating can be classified to two groups which are called “wet beating” and “free beating”. This report deals with the effect of beating conditions on shrinkage of the sheets during drying. Hardwood and softwood bleached sulfate pulps were beaten with a Niagara beater under various conditions of temperature, pulp consistency and load during beating Handsheets made from beaten furnishes were compared with each other in regard to sheet shrinkage during drying and dimensional stability of the sheet. These results obtained are summerized as follows :
1) When handsheets were prepared from unbeaten or slightly beaten pulps, shrinkage of the sheets from hardwood pulp was smaller than that from softwood pulp. As beating was greatly exceeded, shrinkage of the sheets from hardwood pulp increased more evidently than that from softwood pulp.
2) As compared with the sheets made from wet beaten pulps, the sheets from freely beaten pulps shrank more greatly during drying, but showed less stress during its shrinking.
3) Shrinkage during drying was affected greatly by length of the fiber which composed the sheets. That is, sheets composed of comparablly long fibers showed larger shrinking stress but less shrinkage during drying.
4) Pulps beaten freely were shorter in length of fiber than wet beaten pulps of comparable C. S. F. so the sheets made from freely beaten pulps were more unstable in dimensional stabilitythan those from wet beaten pulps. With regard to light scattering coefficient and another physical properties, the difference between the sheets dried with restriction to shrink and those without it was more evident in freely beaten pulp.