One drawback to the full harness is the amount of machinery required to give a large extent of pattern, an upright hook and a needle being required for each thread in one repeat of the pattern. In a half harness only half the amount of machinery is required on the same fineness of cloth to give an equal extent of pattern; but it is only for a few classes of goods that this method of working is suitable, leno curtains and muslins being the principal. Leno curtains will be mentioned under gauzework, as they are wrought with a gauze mounting, but on the half-harness principle. Figured muslin curtains, with a plain ground and coloured flowering, are called ‘crêtes,’ or ‘crête curtains’; these are now generally wrought in a full harness. Figured muslins are much of the same class of cloth, but are not figured with colour and tint for the half harness, known as the ‘common spotting harness,’ or ‘book harness.’ For working them the harness is mounted in the ordinary manner, but only half as many cords are required for it as there are threads of warp. Only half of the warp is drawn into the harness, the other half—every alternate end—passing through it, and being drawn into a plain leaf of heddles, which is hung close in front of the harness. In fine work two leaves of heddles may be used as one, to prevent crowding.
The ground of the cloth is a plain texture, and was formerly wrought by having two leaves of long-eyed heddles in front of the harness, into which all the warp was drawn, this probably being more convenient for the hand-loom weaver; and besides, a more even plain ground can be made with the heddles than with the harness and one leaf of heddles. Two shots of ground, or fine weft, are given to one shot of figuring, or coarse weft, usually cotton rove; but to avoid using a pick-and-pick loom when working by power, the coarse shot may be made by throwing two finer ones into the same shed. In power looms the ground is wrought by raising the plain leaf of heddles and all the harness alternately, and the figuring shed is formed by drawing the harness with a card acting on the machine. The pattern is painted solid, without any twilling or binding on either ground or flower, so that the figuring shot will be in a plain shed for the flower, but will be loose or unbound over the ground, and is afterwards cut off in a cropping machine.
Fig. 109
The plain shed, into which the thick weft is thrown, must also contain the shot of thin weft thrown in either before or after it, according as the figuring shed follows the plain shed made by raising the harness or the heddles; for supposing the heddle shaft to be raised and a ground shot thrown in, then the shed reversed by raising the harness and another ground shot thrown in, then the figure shed formed by raising 50 or 100 hooks of the harness, this opens portion of the last shed, and the figure weft will be thrown in along with the last shot of ground. When both wefts are white this is of but little consequence, but when using coloured wefts for the figure the ground weft would be liable to show along with them and injure the pattern. This was originally overcome by adopting the ‘paper harness’ from the shaft mounting for weaving paper spots. In this mounting two sets of shafts and two harnesses are used, one behind the other. Half of the warp—all the odd numbers of threads—was drawn on the back harness, and the other half—all the even numbers—on the front harness; this would be sufficient to make the cloth, but a pair of leaves of long-eyed heddles were used for working the ground, acting as pressers. On this method of working, a ground and a figuring shot are thrown in alternately, as either half of the warp can be raised by the harness for the figuring shed, and a richer spot is thus given; but still, the rove or figuring shot would fall into the same shed as the ground shot, which may be seen by examining the two spots given in [Fig. 109], A being wrought on the common spot or half-harness mounting, and B on the paper-spot mounting. The grey shots are the ground, and the black ones the figure. However, in the paper-spot mounting it is not necessary to throw the rove into a plain shed; any suitable twill may be used for binding the figure, and will give a much richer effect on one side of the cloth than plain, and tie down the ground shot, which will go into a plain shed.
This principle of mounting is now done away with, as it has no advantage over the ordinary full-harness mounting, which can also have a pair of presser leaves of heddles in front for working the ground, if desired; but they are unnecessary in a power loom, except when a very level ground is required.
A twilled or flushed figure may be formed with the common half harness, but only having half the warp for binding causes it to be loose and ragged round the edges.
To work a large pattern, perhaps the most economical way, at least in the hand loom, is to use a pressure harness with two threads in the mail, and with four presser heddle leaves in front. The number of leaves regulates the twill on the figure. The cloth may be woven pick-and-pick, ground and figure, or 2 picks ground to 1 of figure. When the harness is drawn for the figure all the heddles must be sunk but one leaf, and sinking the two front and two back leaves alternately, raising the back ones when the front ones are sunk, and vice versa, will form plain cloth with the draft 1, 2, 3, and 4 over the leaves. A 4-leaf twilled figure can be made with this mounting, but still it will not have the advantage of the full harness, in which the figure can be varied in twill, and bound round the edges.