Method and apparatus for determining the wet strength of paper

A method of determining the wet strength of paper with an apparatus comprising means for releasing a ball, from a predetermined height to drop freely in a vertical path, clamp means to support a sheet of wet paper and to position the sheet at a predetermined location within the vertical path of the ball and perpendicular thereto, wherein the clamp means includes two discs clamped together to hold a sheet of wet paper therebetween, the two discs having a central axis of rotation, each of the two discs having a plurality of similar sized apertures equi-spaced from and about the axis of rotation, such that the apertures of one disc line up with the apertures in the other disc, wherein the wet paper is positionable between the discs so as to obstruct the apertures, the two discs being rotatably mounted about the axis of rotation such that each of the apertures is positively locatable in the vertical path of the ball, and means for determining speed of the ball dropping in the vertical path below the clamp means, the method comprising the steps of releasing a first ball from a predetermined height to drop freely in a vertical path, aligned with one of the apertures of the clamp means, measuring the speed of the first ball at a predetermined measurement location in the vertical path, positioning the sheet of wet paper in the clamp means in a horizontal plane, the predetermined location of the clamp means being above the measurement location in the vertical path, releasing a second ball having the same size and mass as the first ball, to drop freely in the vertical path and rupture a portion of the sheet of wet paper obstructing one of the apertures, measuring the speed of the second ball after it has ruptured the sheet of wet paper at the measurement location in the vertical path, determining the rupture energy of the sheet of wet paper from the difference in speed between the first ball and the second ball, rotating the clamp means to bring each of the apertures in seriatim into the vertical path and releasing additional balls in seriatim to drop freely in the vertical path and rupture the wet paper obstructing the apertures, measuring the speed of each additional ball after it has ruptured the wet paper obstructing each aperture, determining the rupture energy of the wet paper from the difference in speed between the first ball and each additional ball dropped in seriatim.