Sacking_And_Sack_Manufacture

Sacking And Sack Manufacture. Sacking is a heavy closely-woven fabric, originally made of flax, but now almost exclusively made of jute or of hemp. The more expensive kinds, such as are used for coal sacks for government and other vessels, are made of hemp, but the jute fibre is extensively used for the same purpose, and almost entirely for coal sacks for local house supplies. The same type of fabric is used for wool sacks, cement bags, ore bags, pea sacks and for any heavy substance; it is also made up into a special form of bag for packing cops and rolls of jute and flax yarns for delivery from spinners to manufacturers. Proper sacking is essentially a twilled fabric, in which the number of warp threads per inch greatly exceeds the number per inch of weft. The illustration shows a typical kind of three-leaf twill, double warp sacking. All three-leaf twill sackings are double in the warp, but four-leaf sackings are single. They are usually 27 in. wide, but other widths are made.

The lower part of the illustration shows four repeats of the three-leaf twill, while the lines drawn to the plan of the fabric show that each line of the design is reproduced in the cloth by two warp threads. The weft is single, but each one is usually about four times the weight of the warp for the same length (about 8 lb warp and 32 lb weft). Large quantities of cotton sacks are made for flour, sugar and similar produce: these sacks are usually plain cloth, some woven 

circular in the loom, others made from the piece.

Large quantities of seamless bags or sacks for light substances are woven in the loom, but these are almost invariably made with what is termed the double plain weave, i.e. the cloth, although circular except at the end, is perfectly plain on both sides. Circular bags have been made both with three-leaf and four-leaf twills, but it is found much more convenient and economical to make the cloth for these kinds, and in most cases for all other types, in the piece, and then to make it up into sacks by one or other of the many types of sewing machines. The pieces are first cut up into definite lengths by special machinery, which may be perfectly automatic, or semiautomatic - usually the latter, as many thicknesses may be cut at the same time, each of the exact length. The lengths of cloth are then separately doubled up, the sides sewn by special sewing machines of the Laing or Union make (of which there are seven or eight different kinds for different types of bags), and the ends hemmed. It will thus be seen that the length required is twice the length of the sack plus the amount for hemming the mouth.

The sack is now ready for delivery, unless the name of the owner, some trade mark, or other particulars are required to appear on it. These particulars are printed on in one or more colours by the Kinmond and Kidd patent multicolour sack-printing machine.

The chief centres for these goods are Dundee and Calcutta, all varieties of sacks and bags being made in and around the former city. (T. Wo.)