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Threading Part Two: Sett In A Multi-Heddle World

As you explore more weave structures you will begin to hear the word “density” a lot. This can relate to how you calculate the sett or how you think about the relationship between structure, your materials, sett, and the hand of the fabric.

Calculating Sett Density In A Multi-Heddle World

To achieve various threadings in the multi rigid-heddle world involves cramming the slots which affects sett. To calculate the sett of a multi-heddle threading, you need to take into account this cramming. The density of the sett is expressed as a percentage of the heddle size. For instance, in the point twill threading here, you will achieve 160% of the heddle spacing or size. If you using 12-dent heddles, your sett would be 19.2 (12 x 160% or 1.6). Along the side of this threading you can see the various sett options on different heddle sizes.

Point Twill On Three Heddles at 160% Density


To calculate the threading density, look to a single structural repeat and the number of spaces, or slots and holes, it takes to complete this repeat. This is your “space” count. Then, count the ends in the repeat and add any additional ends that marry in the last space when you place one repeat after another in your end count. Disregard any additional ends threaded for the selvedge. This is your end count.

I find I get the most accurate results if I base my calculations off the back heddle. In the example above, ignoring the additional selvedge thread, there are 6 ends in the repeat threaded over 5 spaces or slots and holes. When you place two repeats next to each other, there are two additional ends threaded in the same slot as the last end of the repeat. The repeat is 1-2-3-4-3-2. In the same slot as the 2 at the end of the repeat, there is also a 1 and a second 2. This makes 8 total ends over 5 spaces. Divide the total number of ends by the total number of spaces, and you get 1.6 or 160%.

As discussed in the previous post, there is more than one way to thread any given structure in the rigid-heddle environment. If you can’t get the sett in this threading, you can  reconfigure the threading, skipping more spaces to put more distance between the crammed areas. (This also applies to a single heddle world, but it is a little more straight forward to figure out.) In the threading below, I can achieve a 112.5% density.

Point Twill On Three Heddles at .75% Density

I can also thread this structure on two heddles achieving either 85% density or 160% density. A dizzying array of options. Notice how in the threading on the right, the 1 is in a slot and on the left it is in a hole. As a rigid-heddle weaver, I have the freedom to assign threading positions any number I like as long as I achieve the order I need. In the case on the right, I can place 1 on a heddle rod and 4 on a pick-up stick. In the threading on the left, I would place 3 on a heddle rod and 4 on a pick-up stick. You could also adjust your materials to suit the sett in your preferred setup, with brings us to our next look at density.

Point Twill On Two Heddles at Two Different Densities


Structure, Materials, and Hand

This could warrant an entirely separate blog post, but it relates to determining these sett choices. I often talk about sett in terms of open, balanced, and close. (In retrospect, “dense” is probably a better word than close.) I prefer these terms rather than assigning a structural name to each density, although there is also logic in that thinking. Twills do perform well on a sett closer/denser than plain weave, but that doesn’t mean you can’t use a variety of densities and get the hand you are looking for. How firm or supple your fabric needs to be, your fiber type and size, and how the yarn is constructed play a substantial role in making your ultimate sett decision. To make these decisions, we often look to sett charts. There is another yarn-centric way to look at determining sett.

Any given yarn will have a maximum and minimum sett where it will perform well. Thomas R. Ashenhurst, a nineteenth-century author of textile books, created a formula that has become known as the Ashenhurst’s rule. It was popularized by creative thinker, Peggy Osterkamp. The basic idea is that a yarn’s sett is calculated based on the size of the yarn and the percentage of the maximum and minimum density this yarn can be sett in either plain weave or twill. These various densities will give you a different hand—ranging from firm to supple.

A new rigid-heddle resource, the Not So Rigid Weaver, has an Ashenhurst’s calculator on her site baed on Peggy’s work. She gave me permission to share this resource with you. Ashenhurst’s formula is based on shaft-loom performance. For the rigid-heddle weaver, it is good to avoid the maximum density recommendations. The crammed slots can get too sticky and the crammed and spaced areas in the woven cloth may not even out in the wash, although you can use this as a feature. The value of the Ashenhurst’s view of sett is that it create a broader range of options than the traditional sett chart.

To see what this looks like in practice, here are three 2/2 point twill samples woven on three heddles at three different densities, using a similar size and style yarn—unmercerized plied cotton, 8/4 Brassard and 3/2 Beam.

2/2 Point Twill Swatching In Three Different Densities 

The swatch on the far left is the most dense, woven on three 12 dent heddles for a sett of 19.2. It has a firm hand and lays flat, perfect for mats. When hung from the line it doesn’t bend, while the other two have varying degrees of suppleness. The swatch in the middle is between firm and flexible making it a nice hand for towels. It is woven on three 10-dent heddles for a sett of 16. The swatch on the far right is the most supple, woven on three 8-dent heddles with a sett of 12.8. This would be good for yarns that shrink a lot and wearables. I created a handout that breaks this down even farther. (Note: it is somewhat easier to weave a 2/2 twill on three heddles than two. Three heddles reduce the occurrence of split sheds. If you thread two you can weave this same structure as a 1/3 twill, which decrease the split sheds, see handout.)

I think I’ll leave it there for now or I’ll be writing an entire book on the subject, oh, wait, I am! Thanks for your patience as I work though this material and to the Yarnworker patrons for supporting the Yarnworker space. By giving you some of the theory sections in small doses, hopefully it will make it easier to absorb the whole.

In April the Yarnworker Patrons and I are going to begin to look at warping two and three heddles. Join us!

Heddles Up!


5 thoughts on “Threading Part Two: Sett In A Multi-Heddle World”

    • Sometimes when using a heddle rod, pick-up stick, or multiple heddles the shed will appear split into more than two layers. Which layer you want depends on the structure and set up you are working with. I have a photo of a split shed at the end of this post.

      As far as blankets, it kind of depends on what kind of blanket you want and the materials you are using. In general a nice hand would be somewhere between firm and supple, so I’d lean more towards the “towel” or “wearables” hand. This is where density + materials becomes a bit of a matrix and a little bit of sampling really pays off if you are designing something from scratch.

  1. This topic is right up my street. For years I’ve been fascinated by the engineering of textiles, and I will happily construct a ‘no thing’ just to see how – or indeed if – it works. At the moment I’m trying to recreate old-fashioned English Aertex using doups, on a home made sample board. We shall see . . . !

    • Sounds fun! Textiles can lead us down so many interesting paths. I love teaching at a science and engineering school (New Mexico Tech). The students are so keen to see how weaving relates to their field of study, or sometimes not. Sometime it is just an escape from thinking too much.


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