Abstract: There are provided a method and an apparatus for determining at least one sheet stretch value of a roll of material. The method comprises the steps of (a) radially marking one side end of the roll from periphery thereof to produce a series of aligned marks along a radius thereof; (b) supporting the roll in such a manner that it is free to rotate, thus allowing relaxation of peripheral layers thereof; and (c) after steps (a) and (b), measuring a lateral shifting value GAP of one of the marks, which is the outermost in periphery of the roll, with respect to an adjacent mark.

Abstract: The method is for producing a first primary roll having a predetermined lateral surface defined by a diameter D.sub.f. The primary roll is made of material wound around a spindle. The material is used to produce smaller secondary rolls of material. The method comprises steps of (a) calculating a portion S.sub.f of the lateral surface, which is covered by the spindle; (b) calculating a portion S.sub.i of the lateral surface, Which represents material needed to produce the smaller secondary rolls of material; (c) calculating a compression factor K1 which is derived from a compression rate K of a previous second primary roll used to produce previous secondary rolls with respect to the previous secondary rolls; (d) calculating D.sub.f where: ##EQU1## (e) winding up material around the spindle to produce the first primary roll until a diameter of the first primary roll reaches said diameter D.sub.f ; whereby loss of material is reduced by taking into account compression factor K1 which varies with respect to time.