Loom
A loom is a device used to weave cloth and tapestry. 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.
Etymology and usage
The word "loom" derives from the Old English geloma, formed from ge- and loma, a root of unknown origin; the whole word geloma meant a utensil, tool, or machine of any kind. In 1404 "lome" was used to mean a machine to enable weaving thread into cloth.By 1838 "loom" had gained the additional meaning of a machine for interlacing thread.
Components and actions
Basic structure
Weaving is done on two sets of threads or yarns, which cross one another. The warp threads are the ones stretched on the loom. Each thread of the weft is inserted so that it passes over and under the warp threads.The ends of the warp threads are usually fastened to beams. One end is fastened to one beam, the other end to a second beam, so that the warp threads all lie parallel and are all the same length. The beams are held apart to keep the warp threads taut.
The textile is woven starting at one end of the warp threads, and progressing towards the other end. The beam on the finished-fabric end is called the cloth beam. The other beam is called the warp beam.
Beams may be used as rollers to allow the weaver to weave a piece of cloth longer than the loom. As the cloth is woven, the warp threads are gradually unrolled from the warp beam, and the woven portion of the cloth is rolled up onto the cloth beam. The portion of the fabric that has already been formed but not yet rolled up on the takeup roll is called the fell.
Not all looms have two beams. For instance, warp-weighted looms have only one beam; the warp yarns hang from this beam. The bottom ends of the warp yarns are tied to dangling loom weights.
Motions
A loom has to perform three principal motions: shedding, picking, and battening.- Shedding. Shedding is pulling part of the warp threads aside to form a shed. The shed is the space through which the filling yarn, carried by the shuttle, can be inserted, forming the weft.
- *Sheds may be simple: for instance, lifting all the odd threads and all the even threads alternately produces a tabby weave. More intricate shedding sequences can produce more complex weaves, such as twill.
- Picking. A single crossing of the weft thread from one side of the loom to the other, through the shed, is known as a pick. Picking is passing the weft through the shed. A new shed is then formed before a new pick is inserted.
- *Conventional shuttle looms can operate at speeds of about 150 to 160 picks per minute.
- Battening. After the pick, the new pass of weft thread has to be tamped up against the fell, to avoid making a fabric with large, irregular gaps between the weft threads. This compression of the weft threads is called battening.
Components
A loom, then, usually needs two beams, and some way to hold them apart. It generally has additional components to make shedding, picking, and battening faster and easier. There are also often components to help take up the fell.The nature of the loom frame and the shedding, picking, and battening devices vary. Looms come in a wide variety of types, many of them specialized for specific types of weaving. They are also specialized for the lifestyle of the weaver. For instance, nomadic weavers tend to use lighter, more portable looms, while weavers living in cramped city dwellings are more likely to use a tall upright loom, or a loom that folds into a narrow space when not in use.
Shedding methods
It is possible to weave by manually threading the weft over and under the warp threads, but this is slow. Some tapestry techniques use manual shedding. Pin looms and peg looms also generally have no shedding devices. Pile carpets generally do not use shedding for the pile, because each pile thread is individually knotted onto the warps, but there may be shedding for the weft holding the carpet together.Usually weaving uses shedding devices. These devices pull some of the warp threads to each side, so that a shed is formed between them, and the weft is passed through the shed. There are a variety of methods for forming the shed. At least two sheds must be formed, the shed and the countershed. Two sheds is enough for tabby weave; more complex weaves, such as twill weaves, satin weaves, diaper weaves, and figured weaves, require more sheds.
Heddle-bar and shed-rod
Heddle-rods and shedding-sticks are not the fastest way to weave, but they are very simple to make, needing only sticks and yarn. They are often used on vertical and backstrap looms. They allow the creation of elaborate supplementary-weft brocades. They are also used on modern tapestry looms; the frequent changing of weft colour in tapestry makes weaving tapestry slow, so using faster, more complex shedding systems isn't worthwhile. The same is true of looms for handmade knotted-pile carpet; hand-knotting each pile thread to the warp takes far more time than weaving a couple of weft threads to hold the pile in place.At its simplest, a heddle-bar is simply a stick placed across the warp and tied to individual warp threads. It is not tied to all of the warp threads; for a plain tabby weave, it is tied to every other thread. The little loops of string used to tie the wraps to the heddle bar are called heddles or leashes. When the heddle-bar is pulled perpendicular to the warp, it pulls the warp threads it is tied to out of position, creating a shed.
A warp-weighted loom typically uses a heddle-bar, or several. It has two upright posts ; they support a horizontal beam, which is cylindrical so that the finished cloth can be rolled around it, allowing the loom to be used to weave a piece of cloth taller than the loom, and preserving an ergonomic working height. The warp threads hang from the beam and rest against the shed rod. The heddle-bar is tied to some of the warp threads, using loops of string called leashes. So when the heddle rod is pulled out and placed in the forked sticks protruding from the posts, the shed is replaced by the counter-shed. By passing the weft through the shed and the counter-shed, alternately, cloth is woven.
Several heddle-bars can be used side-by-side; three or more can be used to weave twill weaves, for instance.
File:SantaMariadelRio145.webm|thumb|upright=2|Using a heddle bar and a shedding stick. See subtitles for a step-by-step. The wide, flat stick is a sword batten; it is inserted lengthwise into each shed, and used to clear the shed, get it wide open and smooth, and to batten. Weaving a silk rebozo with a dyed-warp pattern on a backstrap loom, Taller Escuela de Rebocería in Santa María del Río, San Luis Potosí, Mexico.
There are also other ways to create counter-sheds. A shed-rod is simpler and easier to set up than a heddle-bar, and can make a counter-shed. A shed-rod is simply a stick woven through the warp threads. When pulled perpendicular to the threads, it creates a counter shed. The combination of a heddle-bar and a shedding-stick can create the shed and countershed needed for a plain tabby weave, as in the video.
There are also slit heddle-rods, which are sawn partway through, with evenly-placed slits. Each warp thread goes in a slit. The odd-numbered slits are at 90 degrees to the even slits. The rod is rotated back and forth to create the shed and countershed, so it is often large-diameter.
Tablet weaving
uses cards punched with holes. The warp threads pass through the holes, and the cards are twisted and shifted to created varied sheds. This shedding technique is used for narrow work. It is also used to finish edges, weaving decorative selvage bands instead of hemming.Rotating-hook heddles
There are heddles made of flip-flopping rotating hooks, which raise and lower the warp, creating sheds. The hooks, when vertical, have the weft threads looped around them horizontally. If the hooks are flopped over on side or another, the loop of weft twists, raising one or the other side of the loop, which creates the shed and countershed.Rigid heddles
Rigid heddles can be used without a loom frame or on a single-shaft loom. Odd warp threads go through the slots, and even ones through the circular holes, or vice versa. The shed is formed by lifting the heddle, and the countershed by depressing it. The warp threads in the slots stay where they are, and the ones in the circular holes are pulled back and forth. A single rigid heddle can hold all the warp threads, though sometimes multiple rigid heddles are used.Treadles may be used to drive the rigid heddle up and down.
Non-rigid heddles
Rigid heddles or are called "rigid" to distinguish them from string and wire heddles. Rigid heddles are one-piece, by non-rigid ones are multi-piece. Each warp thread has its own heald. The heald has an eyelet at each end and one in the middle, called the mail,. A row of these healds is slid onto two staves, the upper and lower staves; the staves together, or the staves together with the healds, may be called a heald frame, which is, confusingly, also called a shaft and a harness. Replaceable, interchangeable healds can be smaller, allowing finer weaves.Unlike a rigid heddle, a flexible heddle cannot push the warp thread. This means that two heald frames are needed even for a plain tabby weave. Twill weaves require three or more heald frames, and more complex figured weaves require still more frames.
The different heald frames must be controlled by some mechanism, and the mechanism must be able to pull them in both directions. They are mostly controlled by treadles; creating the shed with the feet leaves the hands free to ply the shuttle. However in some tabletop looms, heald frames are also controlled by levers.