A loom is a machine or device for weaving thread or yarn into textiles. Looms can range from very small hand-held frames, to large free-standing hand looms, to huge automatic mechanical devices.
In practice, the basic purpose of any loom is to hold the warp threads under tension to facilitate the interweaving of the weft threads. The precise shape of the loom and its mechanics may vary, but the basic function is the same.
The earliest weaving was done without a loom, but in general the supporting structure of the loom is called the "frame". The frame provides the means of fixing the lengthwise threads, called the "warp", and keeping them under tension. When producing a long piece of material, the warp threads are wound on a roller called a "beam", and attached to the "cloth beam" which will serve to hold the finished material. Because of the tension the warp threads are under, they need to be strong, and the strengthening process (using flour and water paste) was called "dressing". The warp was originally made of flax which makes linen until the spinning process was refined enough to provide strong cotton yarn.
The thread that is woven through the warp is called the "weft" or "woof". The weft is threaded through the warp using a "shuttle", which carries the weft through separated warp threads. The original "hand-loom" was limited in width by the weaver's reach, because of the need to throw the shuttle from hand to hand. The invention of the "flying shuttle" with its "fly cord" and "picking sticks" enabled the weaver to pass the shuttle from a box at either side of the loom with one hand, and across a greater width. The invention of the "drop box" allowed a weaver to use multiple shuttles to carry different wefts.
With the hand freed by the use of the flying shuttle, the weaver can operate the "lathe" suspended from the frame. The lathe holds the reed comb used to beat (compact) the woven weft.
Rather than having to lift each thread individually, alternate threads can be separated by introducing a bar between the threads: the gap created is called the "shed". While an inserted bar only presents one orientation, alternating sets of threads can be lifted by connecting them with string or wires called "heddles" to another bar, called the "shaft" (or "heddle bar" or "heald"). Heddles, shafts and the "couper" (lever to lift the assembly) are called the "harness" — the harness provides for mechanical operation using foot- or hand-operated "treadles". (Multiple harnesses can be used, connected to different sets of warp threads in a "draw-loom".)
"Sleying" is the process of threading the warp yarn through the reed. Usually one speaks of "sleying the reed". You "set" (verb) the warp at X ends per inch and then you can say that its "sett" (noun) is X ends per inch.
Types of Looms
The earliest looms were probably vertical Warp-Weighted Looms, with the warp threads suspended from a branch or piece of wood and weighted or attached to the ground. The weft threads would be pushed into place by hand or a stick that would eventually become the shuttle. At first, it was necessary to raise and lower every warp thread one at a time, which was a time-consuming and laborious process. Basic techniques, such as the insertion of a rod, were developed to produce a shed, the space between warp threads (perhaps every other thread would be alternately raised and lowered), so that the weft thread or shuttle could pass through the entire warp at once.
On a horizontal Ground Loom, the warp would be strung between two rows of pegs. The weaver would have to lean over in order to work, so pit looms were developed, with the warp strung over a pit, so the weaver could sit with his or her legs underneath and would then be on a level with the loom.
Frame Looms followed basically the same principles as ground looms. The loom was constructed out of sticks and boards attached at right angles (producing a box-like shape), which meant that it was portable and could even be held in the weaver's lap. Frame looms are still in use today, usually as a portable, less expensive, and compact alternative to a table or floor loom.
Backstrap Looms, as the name implies, are tied around the weaver's waist on one end and around a stationary object such as a tree, post, or door on the other. Tension can be adjusted simply by leaning back. Backstrap looms are very portable, since they can simply be rolled up and carried.
Foot-Treadle Floor Looms
Handweavers today tend to use looms with at least four "shafts" or "harnesses". Each shaft contains a set of "heddles" through which yarn can be threaded (and attached, through a variety of mechanisms, to the front and back beams of the loom), and by raising the harnesses in different combinations, a variety of patterns can be achieved. Looms with two such shafts are called "rigid heddle" looms and variants with eight or more shafts are available.
The shafts on a Floor Loom are controlled by a series of foot pedals (called "treadles"). This is an important development, since it keeps the weaver's hands free to manipulate the shuttle and it is easy to raise and lower warp threads in selected combinations. As the material is woven, it can be wrapped around the front beam, as unwoven yarn is unrolled from the front beam, so length is not limited by the size of the loom. A Table Loom is similar, but, as the name suggests, it is smaller and equipped with levers rather than treadles, since it is made to sit on a stand or on top of a table.
The first Power Loom was built by the Englishman Edmund Cartwright in 1785. Originally, powered looms were shuttle-operated but in the early part of the 20th century the faster and more efficient shuttle-less loom came into use. Today, advances in technology have produced a variety of looms designed to maximize production for specific types of material. The most common of these are air-jet looms and water-jet looms. Computer-driven looms are now also available to individual (non-industrial) weavers.
The Jacquard Loom is a mechanical loom, invented by Joseph Marie Jacquard in 1801, which used the holes punched in cardboard punch cards to control the weaving of patterns in fabric. The loom enabled even amateur weavers to weave complex designs. Each punch card corresponded to one row of the design and the cards were strung together in order.
Each hole in the card corresponds to a hook, which can either be up or down. The hook raises or lowers the warp thread so that the weft will either lay above or below it. The sequence of raised and lowered threads is what creates the pattern. Each hook can be connected to a number of threads, allowing more than one repeat of a pattern. A loom with a 400 hook head might have 4 threads connected to each hook, giving you a fabric that is 1600 warp ends wide with four repeats of the weave going across.
The Jacquard loom was the first machine to use punch cards to control a sequence of operations. Although it did no computation based on them, it is considered an important step in the history of computing hardware. The ability to change the pattern of the loom's weave by simply changing cards was an important conceptual precursor to the development of computer programming.
The term "Jacquard loom" is a misnomer. It is the "Jacquard head" that adapts to a great many dobby looms such as the "Dornier" brand that allow the weaving machine to then create the intricate patterns.
Jacquard looms, whilst relatively common in the textile industry, are not as ubiquitous as dobby looms which are usually faster and much cheaper to operate. However unlike jacquard looms they are not capable of producing so many different weaves from one warp. Modern jacquard looms are computer controlled and can have thousands of hooks. And inevitably, unlike Jacquard's original invention there is now no need for the use of punched cards - instead the patterns are literally computer controlled. The threading of a jacquard loom is so labor intensive that many looms are threaded only once. Subsequent warps are then tied in to the existing warp with the help of a knotting robot which ties each new thread on individually. Even for a small loom with only a few thousand warp ends the process can take days.
A Dobby Loom is a loom in which each harness can be manipulated individually. This is in contrast to a treadle loom, where the harnesses are attached to a number of different treadles depending on the weave structure.
Dobby looms allow a variety of complex weave structures on one threading. A Jacquard loom is an example of an adaptation to a dobby loom. The harnesses can be controlled by a computer or a series of pegs which allow them to rise or fall.