Page:Paper and Its Uses.djvu/98

86 to take effect, consequently the majority of the fibres are parallel to the direction of the flow of the pulp. Some fibres are crossed or felted; but taking the web of paper, it is more easily pulled apart across its width than in the direction of its length. The fibres are fixed and are dried in a state of tension, so that the fibres in the direction of the flow (known as the machine direction or the grain of the paper) are fully extended, and subsequently expand but little in length, but may do so in width or diameter.

The direction of the fibres serves to distinguish between hand- and machine-made papers. Tearing a piece of hand-made paper will result in ragged tears, very similar both ways of the sheet. A piece of machine-made paper shows a ragged tear in one direction, and a much straighter tear in the other. The straighter tear is in the machine direction. If a circle about three inches in diameter is cut from a hand-made sheet and thoroughly damped on one side, the paper will curl slowly and unbend again. If a similar piece is cut from machine-made paper and treated in the same way it will curl more quickly into a cylinder and remain rolled up for some time. This not only serves as a distinction between the two papers, but, in machine-mades, shows the machine direction which is parallel to the axis of the cylinder of paper. By marking the sheet before the circle is cut, the machine direction of the sheet can be determined.

Strips cut from the sheets, one from each way, 7 inches long by I inch wide, held between the finger and thumb and allowed to incline at an angle of 60°, will behave differently according to the method of manufacture. Hand-made strips will keep together, because the fibres are equally distributed, while strips of machine-made paper will separate, owing to the difference in