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Jack Looms - part 2

by Joanne Hall

•   Achieving a larger shed, better selvages, avoiding warp skips
      and preventing broken warp threads

•   Adjustments you can make to your jack loom
•   Benches
•   Bibliography

Achieving a larger shed, better selvages, avoiding warp skips and preventing broken warp threads
These are common weaving problems with small looms. The simplest way to get a large shed on a jack loom is to loosen the tension, but that can create poor selvages. Tightening the tension makes the shed small and causes warp skips.

"Because of the position of the closed shed below the warp line, there is a tendency for the shafts to float or hang suspended on a tight warp. Such a condition is the major cause for warp skips when a tight warp is woven with this shedding motion." Fannin p.80

To understand this problem, note that the shafts on a jack loom need to be resting several inches below the breast beam. When a shaft is raised, it must rise to a height which is the same distance above the breast beam. The tension must be kept loose in order to keep the resting shafts down. If the resting shafts do not stay down, the threads on them will become loose, making it hard to throw a shuttle. This gives the shuttle the opportunity to catch threads on the wrong side of the shuttle, causing skips and floats in the weaving. It also results in poor distribution of the weft and poor selvages. Wide warps exaggerate the problem. It is also difficult to weave weftfaced weaves as every other warp thread is loose.

To make the tension tighter, improve selvages and to keep the shafts from rising, you will need to weight the shafts, or use some other method to adjust your loom. To achieve better selvages, you can weight your selvage threads with a weight hanging off the back beam behind the loom. The selvage threads are not beamed and the weight makes them tighter than the rest of the warp. If this tighter thread makes the shafts rise, then take this thread out of the heddles. You may have heard that jack looms are harder on warp threads and cause more broken ends. Resting shafts hold the warp threads down with the metal heddles. As warp threads are raised, they loosen as they reach the center of the shed. Then they tighten again as they reach the top of the shed. The constant loosening and tightening of the warp threads creates a snapping of the warp, which can cause some stress. On a jack loom, when a warp is not treadled, it is at maximum tension. This can cause extra stress on the threads.

When you are not weaving you should loosen the tension on the warp as there is added stress at the point where the threads are held in the metal heddles. And when you are weaving, advance the warp frequently to change the position of the metal heddles on the warp. If broken threads occur at the selvages, use a temple.

On counterbalance looms, the warp is looser when it is at rest. When a shed is made, the threads only move half the distance they move on a jack loom and there is no loosening before the warp become tight.

Loose tension on the bottom of the shed does not support a shuttle very well, so the shuttle can easily fall through the warp threads. Because of this, a shuttle race is added to the beater of a jack loom to hold the shuttle. This can interrupt rhythm as the shuttle needs to be placed on the shuttle race and the shuttle race can get in the way of your hand. Counterbalance and countermarch looms do not have shuttle races unless they have fly shuttles. This is because the bottom of the shed is very tight. If you try to tighten those threads on the bottom of the shed of a jack loom by tightening the tension, the tension is increased on the top of the shed, making treadling more difficult. The bottom of the shed stays looser.

The list of adjustments will give you some ways to solve these problems. Don't blame yourself, but rather, try to find a solution for your loom.

Adjustments you can make to your jack loom
When you start weaving, look for ways to adjust your loom to achieve clear sheds and easy treadling. Weave a couple inches, put on a temple (stretcher) to maintain the width, and adjust the tension to get a good separation of the warp threads. Open a shed and feel the tension on the top of the shed. Then feel the bottom of the shed. The tension should be the same. If it is looser on the bottom of the shed, you may need to try some adjustments to your loom.

The following suggestions will be helpful when you are weaving difficult warps. Try them in the order given, until you have a clear shed, sufficient tension and easy treadling. Note: These suggestions are for jack looms. If you have a counterbalance or countermarch looms, only numbers 1, 5, 7 and 10 apply to your loom.

  1. Treadle tie ups may need to be adjusted to get a better shed if the top of the shed is uneven.

    If some threads are being raised too high, determine which shaft is rising too high, untie the cord or the treadle attachment and make it longer. If the shaft is not rising high enough, shorten the tie. Check each treadle to make sure that all the shafts rise to the same height. If the lower part of the shed is not even, the problem must be solved with numbers 4 or 8.

    "The most objectionable feature of nearly all looms of this type is not so much the lower speed and therefore inferior performance, but the impossibility of adjusting the lower part of the shed." S. A. Zielinski vol.2 p.30

  2. Tie up your treadles to raise only one shaft and treadle with both feet at once.

    If you are working with a warp that doesn't want to separate when you press on the treadle, either because it is a fuzzy warp, or is sett very close as with double weave or warp faced weaving, you can try tying the treadles each to only one shaft. Then treadle one at a time, raising fewer warp threads with each foot. This would then be slow to weave and would interrupt your rhythm. It also takes longer to memorize the treadling sequence, so you might want to try some other adjustments first. For very difficult sheds, try using a batten to clear the shed and hold it open.

  3. Treadle springs can be added to keep the weight of the treadles from pulling on the lamms, which then push the shafts up.

    These springs are very easy to install at the ends of the treadles. You will need to add a rod to the back of the frame where the shafts are. From this rod you attack one spring for each treadle. These springs do not pull on the shafts and they are not attached to the shafts. They merely hold the treadles up and sometimes this is all that is needed to have a better shed. After you begin to weave, attach the springs which are needed to keep the shafts from rising when they are supposed to stay down. You may not need to attach all of them. These springs are standard equipment on Leclerc jack looms with more than four shafts.

  4. Adjust the height of the beater.

    On some looms the beater is made so that it is adjustable in height. On a counterbalance loom, the beater is positioned so that the warp threads pass through the center of the reed. On a jack loom the warp threads rest on the bottom of the reed. Jack looms have shuttle races because the weaving is done on a looser tension and the shuttle race is needed to support the shuttle as it is thrown across the warp.

    The lower part of a jack loom shed is sometimes not even. You cannot see this as the beater corrects the difference. The bottom of the reed and the shuttle race are holding all the threads up to one level. The beater must be high enough to hold the threads up. If the bottom of the shed will not stay down and some threads do not lie on the shuttle race, raise the beater. If the beater is holding the warp threads too high, the resting shafts will rise. In this case the beater should be lowered. If the beater is too high, the reed may be adding too much friction to warp threads. If you are working with fragile threads, you may want to lower the beater and place a smooth dowel under the warp threads directly behind the beater. It needs to be at a height which holds the warp threads just above the bottom of the beater. This will decrease the amount of friction put on the warp while beating.

    "We shall risk here a statement that the reason why so little weaving with fine yarns, single linen, etc. is done in North America is that there are too many jack-type looms on this continent." S.A. Zielinski vol.2 p.30

    "One of the most serious disadvantages to the push-up system is the wide gauge required.......well over ½" per shaft. A set of four shafts occupying a space of 6½-7" is not uncommon." Fannin

    You might also add foam rubber or a cushioning material under the first and second shafts, so that they rest a little higher than the other shafts. This will help to even the bottom on the shed so that you can lower the beater. It may also alleviate some of the noise of the shafts falling down to the jack box.

  5. Extend the back of the loom to increase the depth of the loom.

    On some looms this can be done very easily by replacing only one part of the frame on each side of the loom. On other looms it may not be possible without major carpentry, but it is worth a try if your loom is shallow. Any extra depth that you can get will give you a better shed and easier treadling.

    "The frame should ordinarily be longer from front to back than from side to side, to provide ample weaving space. If the frame is very shallow it is impossible to weave more than an inch or two without releasing the tension and winding up the web, which is a nuisance. Also undue strain is put on the warp when the sheds are opened." Mary Atwater p.32

  6. Raise your back beam.

    This can be helpful if you cannot make your loom deeper. It is easy to check to see if this will help by simply checking your tension. After beginning to weave, press down on a treadle and feel the tension on the top and the bottom of the shed. If the tension on the top of the shed feels tighter then the bottom, then loosen your tension. Add a stick onto the top of your back beam, and re-tention your warp. If this makes the tension more even, tie the stick securely to keep it in place and continue to weave. You can try different thicknesses of wood, but be sure that the stick is very smooth. Many very old counterbalance looms had the back beam several inches higher than the breast beam for more comfortable weaving.

  7. Leave your lease sticks in the warp near the back beam.

    Lease sticks are left in the warp near the back beam by many weavers. This makes it easier to repair broken threads but it also eliminates any twists in the warp, allowing the sheds to open more freely. But if your loom is not very deep, there may not be enough space to leave the lease sticks in. They will shorten the distance from the shafts to the back of the loom. If you have twists in your warp, insert the lease sticks periodically and wind your warp forward, carefully easing the sticks along to take out the twists. Then remove the sticks and rewind the warp onto the warp beam. You can try to place the lease sticks between the back beam and the warp beam, but if you have some twists in the warp, it may not work to leave them here. The next time you beam your warp, beam with the least sticks left in the warp. Hold the warp at tension while beaming and ease the lease sticks along as you wind the warp on.

  8. Adding weights to your shafts can be helpful.

    If your resting shafts will not stay down, you can tie a metal rod onto the top of the shafts which need extra weight. These can be added even after you have begun to weave. The added weight should be removable, as your next warp may not need it, or it may be needed on a different shaft. This extra weight results in more difficult treadling, as you will be lifting more weight. Heavier shafts may also be more wearing on fragile warp threads.

    If you have extra metal heddles, you can put them on the shafts, an equal number on each side. You must put them on before you begin threading the loom, so you need to know which shafts will need the extra weight. This is easy on a balanced weave as you can put an equal number on each shaft. On an unbalanced weave, add them to the shafts which hold the most threads and are tied to the most treadles.

    Another way to weight the shafts is to use an extra treadle. The treadle can have a weight added if the treadle is not heavy enough. The shaft is attached directly to the treadle, which must be one of the center treadles. This treadle is not used for weaving, except to pull down a shaft if it doesn't fall all the way down. If your jacks are beneath your shafts this may only work on the first or last shaft. Please note that some jack looms already have heavy shafts.

    "Single tie-up jack-type if used at all, should have adjustable weights attached to each heddle-frame....the more heddles on a particular frame, the more weight." S.A. Zielinski vol. 2 p.13

  9. Adding springs or bungie cords at the bottom of the shafts can help to hold them down.

    If you have trouble with a shaft on an unbalanced weave, this can be a good solution as sometimes the added weight on the shaft isn't enough. You can attach the spring just to the shaft which needs it. If your loom has jacks under the shafts, you may only be able to do this to the first or the last shaft. If the jacks are at the top of the loom, installing springs is very easy and they can then be removed when not needed. This is important since you will have to treadle against this spring, making the treadling harder for that shaft.

    "Power looms using a positive spring return for lowering the shafts do not have to be concerned with this (heavy treadling) because there is enough power available for overcoming the added resistance. On a foot-powered handloom, anything that makes the shedding motion heavy and slow to operate works against the weaver....Weights, therefore, seem to be the best solution where springs would render the harness motion too heavy to operate." Fannin p.80

    Use a double tie-up, i.e., tie a cord direct from the harness frame that you wish to remain full down to the treadle that is in the full down position. (When this treadle is then depressed, it will raise the frames you have normally tied up and also drive the additional tied harness frames down.). Use of any of the above procedures will cause the treadling action to be heavier and slower." Leclerc p.21

  10. The use of a stretcher (temple) will solve some selvage tension problems and make beating easier.

    Preventing draw-in by using a stretcher not only keeps your selvage warp threads from breaking, but allows you to beat in your weft without so much force. Without a stretcher you are beating against the drawn in warp threads, which are holding the beater away from the fell line. This alone can solve some problems. Stretchers are recommended for all weaving except tapestry and some warp faced weaving.

  11. Remove the shuttle race if you want to develop a better rhythm.

    If your shed is clear, you have heavy shafts and a fairly tight tension, try removing the shuttle race. If it is an added part of the beater, simply remove the screws which hold it on. If it is a solid part of the beater, you would have to have a new piece made for the lower part of the beater. On some looms you may also simply turn it around, so that the shuttle race is behind the beater.

  12. Difficult warps can be sized.

    A warp that you know will be difficult to weave because it is fragile, fuzzy, or a hand spun yarn, can be sized before it is beamed. Gelatin, hide glue, cooked flax seed or cooked cornstarch can be tried. If you have a warp which is already on the loom, you could try a soluble oil, spray starch, silicone spray, or Johnson & Johnsons No more Tangles. With linen water is helpful.

  13. Weight the beater.
    When you want a tight beat, you can place a metal rod under the beater to add weight to the beater. This weight should be removable. A weighted beater may not necessary if the suggestions above have been tried. For instance, it is more important to use a stretcher (temple), than to weight the beater.

The suggestions above are to be tried only after you know that you have put your loom together properly and that all parts are in good working order. Metal parts should not be dirty or rusty, the frame must be securely assembled and tight and all the wooden parts are smooth. Warps must always be centered; extra heddles if left on the shafts must be divided equally so that there is the same number of heddles on each side of the shaft. Heddles need to be put on properly, and use no more than 10 metal heddles per inch per shaft; more than this requires string heddles. Warp tension must be the same all across the warp. Contact the loom maker if you think there are problems with the loom. Most companies supply replacement parts even for discontinued looms.

A word about benches
When you have to put a lot of pressure on treadles as you would if raising many shafts, you tire more quickly, and are less comfortable on your bench. Make sure the bench is the right height for you. Try padding your bench and make sure to place the bench as close to the loom as possible so that you are sitting on it and not teetering on it. If your bench is not close enough, you will be off balance as you are trying to press down on the treadles and you will not be in a good position for weaving. You should also tie up the treadles at a good height for you. Learn to make yourself comfortable during all phases of weaving.

"A bench seat that is part of the loom and stretches its full width is preferable to a separate stool." Peter Collingwood p.52-53

Bibliography:
Atwater, Mary, The Shuttle-Craft Book of American Hand-Weaving,
      Macmillan Publishing Col, Inc., NY, l928, l975
Brassard, Francois, http://www.leclerclooms.com/
Brown, Rachel, Spinning, Dyeing and Weaving, l980
Chandler, Deborah, Handwoven Magazine, March l988
Collingwood, Peter, The Techniques of Rug Weaving,
      Watson-Guptill Publishing, NY, l969
Fannin, Allen A., Handloom Weaving Technology, Van Nostrand Reinhold Co. NY, l979
LaLena, Constance, Handwoven Magazine, Sept. l984
Leclerc, Robert, Warp and Weave, Nilus Leclerc Inc., Quebec, l979
Thorpe, Heather, A Handweavers Workbook, Collier Books, l956
Tidball, Harriet, The Weavers Book, The Macmillan Co. NY l961
Tovey, John, The Technique of Weaving, Scribner, NY, l965
Zielinski, S.A., Robert Leclerc, ed., Master Weaver Vols 1,2,6, Nilus Leclerc, Inc.,1979


 

Part 1

Joanne Hall has been teaching weaving for many years, first at the University level and then at her own Elkhorn Mountains Weaving School in Clancy, MT. Joanne's range of work ranges from finely-woven Swedish textiles to large tapestry commissions. In 1996 Joanne received the MAWS Living Treasure Award. Joanne is active in the Helena Weavers Guild, ANWG and HGA.

Copyright © 1998 by Joanne Hall. Please contact the author for permission to use any part of this article.

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