Jacquard Weaving and Designing

by T. F. Bell

The term ‘split harness’ is sometimes applied to the pressure harness when wrought with two threads in the mail, this constituting a splitful of warp, so that each cord of the harness controls a splitful of warp; but this is only the finest description of pressure harness.

Fig. 110

The split harness, or ‘shaft monture,’ was invented in the silk district of Bethnal Green, shortly after the introduction of the jacquard, for weaving rich silks which have about 400 threads of warp per inch, but much less weft—perhaps about one-fifth of that number of threads. The harness is wrought with the ordinary jacquard, but there are two mails and lingoes attached to each neck cord, as shown in [Fig. 110]. A, A are the neck twines, B is the cumber board, and D the mails. If this mounting were wrought with the jacquard only, it would produce the same effect upon the cloth as if two threads were drawn into each mail of an ordinary harness. This would, of course, take away the fine appearance of the cloth. To avoid this a set of shafts, C, C, are passed through loops in the twine above the mails, and are attached to a set of hooks in front of the jacquard, or at each side of it, or may be wrought by a separate dobby. Twenty-four shafts are mostly used, and are usually flat enamelled iron bars. These shafts are for working the ground of the cloth, and can raise each row of mails separately, as shown at No. 1 leash, thus splitting the pairs of threads that are connected with each hook of the jacquard. One or more of these shafts, according to the texture required for the ground, are raised at the same time that the jacquard draws the figuring shed. No ground texture is put on the pattern for the cards, but the figure must be twilled, or have the binding marks cut on the cards for it. The binding of the figure will be in pairs of threads—that is, two threads of warp must sink together under a weft shot, though on the design these two threads will appear as one, as they are wrought by the same hook of the machine. On account of the number of warp threads, rising and sinking in pairs will not much affect the appearance of the figure; though it must be coarser than if the threads were bound separately, and will also have a rougher or more ragged outline; but to get a large figure with so much warp would necessitate a great amount of machinery if the threads were drawn into separate mails with one to each cord of the harness.

This method of working is surpassed by the twilling machines now in use (see Twilling Jacquards), though they are more intricate, and would not suit well for a hand loom, as they are heavy to draw.

PRESSURE HARNESS

This is the old draw-loom system of working, and, old as it is, is still in use on our modern hand and power looms on the finest description of damasks, and is not likely to be surpassed for making a good piece of cloth. Much firmer than a harness, and producing the largest possible pattern with the least possible cards, mounting, and machinery it took up its position in the days of the drawboy, and has held its own, with the aid of the jacquard, against all the inventions of modern times. The principal advantage of this system of working is that a much larger pattern can be produced with the same quantity of cards, mounting, and machinery, than by any other means; but the pattern wrought by a pressure harness will not compare with one wrought by a full harness for fineness of outline or detail. When weaving large tablecloths with 100 or 120 threads of warp per inch, and from 50 to 72, or even 90 in. in the single pattern—that is, when the pattern is all, or nearly all, single—the amount of machinery that would be required to work it on a full harness could not be crowded on a loom, the French system being the only one by which it might be attempted; and even then the difficulty of keeping the machinery and cards in perfect working order would be very great, not to mention the cost of mounting, patterns, cards, &c. The quantity of harness and machinery is reduced in a pressure harness by drawing two or more warp threads into each mail in the harness. Suppose we take 60 in. of cloth with 100 threads per inch = 6,000 threads, and allow 3 threads to each mail in the harness, or each hook of the jacquard, 2,000 hooks, or four 500 jacquards, would be required to work the pattern. As many as six 600 jacquards are sometimes required on this description of work when very fine; but three or four 500 or 600 machines are more commonly used on either hand or power looms. To work one of these finest patterns in a full harness 10,800 hooks would be required—say, six 600 machines with 3 threads to each mail = 10,800; and almost double this number of cards, even with working them backwards and forwards, would be necessary.

In early times, when the drawboy took the place of the jacquard, 6, 8, or 10 threads were put to each mail, or went to what would now be one hook of the jacquard; and patterns were not usually so extensive as they are now, so that the cords of the harness were greatly reduced in number, but with a proportionately coarser effect of pattern. The difference between a pattern wrought with a full harness and one wrought with the pressure or any of the twilling harnesses, is that the outline is clear and defined in the full harness, and the detail and points of the figures can be turned on a single thread, whereas in the others the edges of the figures will be jagged or in steps, and the points must turn on whatever number of threads are lifted together. The pattern on the cloth must therefore have somewhat of the rough, square effect of the design on point paper, though, of course, reduced in size, but will be worse in this respect—viz. that whereas the edges of the figure on the point paper are clear and well defined, on the cloth they are not so, the rough edges to some extent blending the figure into the ground, and not giving the clean, sharp effect of a full-harness pattern. Shaded effects are also coarse on a pressure harness, but can be made effective if broadly treated. Cloth with 100 or 120 threads per inch does very well to have three threads to the mail, and from 80 to 100 threads per inch suits very well for two to the mail. Any coarser set than 80 threads per inch requires to be woven in a full harness to produce good work, and for superior work nothing less than 100 threads per inch should have two threads to the mail, though 80 per inch does very well.