A shedding device is a device that makes a shed. What is a shed? It is the space between raised and lowered warps on a loom.
A shedding device makes that shed. There are many different types of mechanisms to do this and not all are equal. Here are a few examples that people use for tapestry weaving.
Mirrix Shedding Device
A Rotating Heddle Bar
Let's start off with a really simple example of a shedding device. I had one of these at one point. They seemed to be called a "rotating heddle bar". I don't remember it being terribly useful, but then again I was using it on a loom such as this one with lousy tension. I imagine it would be easier to use on a loom with great tension. The concept is simple. You have two sets of slots. When you turn the device one way it raises one set of warp threads. The other way, it raises the other set of warp threads.
Such a shedding device can be used at only one set. This makes sense since simple frame looms often provide just one set. Other downsides: The shed is small and the warps can pop off of the bar.
Here's an example of a rotating heddle bar.
A Rigid Heddle
Next on the list of shedding device is the rigid heddle. It consists of holes and slots. When you lift the rigid heddle, the warps that go through the holes are lifted. When you press down on the rigid heddle, those same warps are lowered. This works well for making cloth but is rather a disaster when it comes to tapestry. Why? Because the warps that go through the holes, when lifted, are under more tension than the warps that lie flat and go through the slots. What happens is the overall tension is not enough and internal picks can get off because you are variously wrapping around tight and loser warps.
This is a clearer view of what the rigid heddle looks like. You can get them in a variety of setts.
Here is an example of a rigid heddle on a rigid heddle loom.
High Warp Shedding System
Next, let's move on to high warp shedding system. This is used on vertical looms only. There is a bar on which one puts heddles that attach to every other warp thread. The other set of warp threads is raised with a shed stick. You don't pull on all the heddles at once. They are used by pulling down on some of them with your hand. You can only grab so many with your hand. I have never used this kind of device so will not comment. It is absolutely a tapestry-based shedding device so therefore is clearly appropriate for weaving tapestry.
Here is an example of a high warp shedding system.
Navajo Shedding System
Can't forget the Navajo system of creating a shed. It's really almost identical to the high warp system. But instead of a fixed bar on which to put the heddles, heddles are on a bar that just hangs in place. The difference is, you actually lift the whole bar and then stick a shed stick in the shed to hold the shed open. This is only for one set of warps. The other set has a permanent bar just above the stick with heddles. To use that just pull it down (it lives out of the way at the top of the loom) so it's right above the bar with heddles. This will give you just enough room to insert a shed stick. And yes this operation seems to be one of the most time-consuming. It makes sense that these tapestries are woven on the fell line. So one changes the shed and then weaves all across. You can see how building up shapes would be really time-consuming. And some of the best Navajo techniques (weft interlock for example) are dependent on building up all the wefts at the same time or, better said, weaving on the fell line.
This video is an example of how the Navajo shedding system works.
Double Bar Shedding System
Our next option doesn't have a name that I know of. It's pretty simple. You have two or more bars (four if you want to do more complex weave structures) that in the resting position are held in a neutral position. Just like the high warp loom, the warps are attached to these bars with heddles. When you want to raise the warp threads pull one bar forward and rest it on the holder that allows for this. It's similar to how you use a rigid heddle. But the difference is, both sets of warp threads are held at the same tension. Although this method is very different from what we use on the Mirrix, it is similar in that both are considered counter-balance looms. What is that, you might ask? It just means that all the warp threads are held at the same tension and that the ones you are raising have a stopping point.
This video shows an example of this shedding system.
Counter-Balance Shedding System
This next one is fancy. I in fact used to own this loom. It was my first tapestry loom and I adored it. Eventually, I discovered that the largest Mirrix Looms was just as appropriate for my needs as this studio-claimer. So I passed it on to someone else who I am sure loves it dearly. It employs a standard counter-balance shedding system. There are two shafts which hold the heddles (wire, in this case). When you press the treadle, one set of heddles raises half the warp threads but the other set gets depressed so that the tension is the same for all the warp threads. Of course, warping this loom takes an entire day. And although I loved this loom (we always love our first really good piece of equipment when we've suffered with inadequate equipment for so long) it had tension issues which I was able to fix with some angle arms and sandpaper. It is a dedicated tapestry loom.
The Mirrix Shedding Device
Gosh and that leads me to the last option for shedding devices that are employed by tapestry weavers: the Mirrix Loom. I found a picture of it on the internet! The warp threads are attached to bars on either side of the shedding device. When the shedding device is rotated, one set of warp threads is raised. The shed is not huge because the tension is (and should be) very tight on a tapestry loom. There is a limit to how much you can raise the warp threads. However, the shed is clean and stays open while you weave. It can be used at any sett. You can even put on more than one shedding device for more complex weave structures. The Mirrix shedding device can also be operated with an electric treadle.
For a diverse and fully functional shedding system, you really can't beat the Mirrix.
Ready for your first Mirrix Loom? Not sure which one to choose for your needs? Click here to get a free and personalized loom recommendation!