I've been spinning and ciphering, measuring and mulling over metres of yarn the past few days. It began with a question and then some comments on a fibre internet site and a discovery on my part that not all spinners measured their yarns in the same way. I realized that for all the time I've been spinning, I'm still making assumptions about yarn and its properties which I have not tested for myself. This will not do.
So, out came the reference materials, stacks of books and magazines back to the late l970's and '80's. I read about twist and twist calculations, thought about theories and mathematical formulae by such spinning luminaries as Alden Amos, Rita Buchanan, Allen Fannin, Anne Field, Mabel Ross, and Peter Teal. I looked up practices by contemporary spinners such as Jacey Boggs and Jillian Moreno. Since I'd always been told that the formulae for calculating twists per inch in hand spun yarn were based on industrial standards, I looked those up, too. (Yikes, by the way! If you're a math geek, which I'm not, you'll love clicking to this site. Me, not so much.) I spun some yarn, measured it, finished it, then set up a laboratory of yarn measuring tools on the kitchen table and measured again. I checked and rechecked my calculations. I called in a consultant-Mr. DD, who knows very little about yarn twist, but who does know a lot about tools-and I asked him to do some yarn measurements based on the instructions given with a particular tool.
These are the yarns I spun, using generic wool roving in black and white. From left to right, there is a skein of white singles, with a black tracer yarn, a black singles with a white tracer, a 2 ply spun with equal amounts of spinning and plying twist, a 2 ply with twice as much plying twist as spinning twist and a 2 ply with half as much plying twist as spinning twist. All yarns were spun Z and the plied yarns were plied S. While I didn't spin to a standard, I did measure my drafting length (12 inches), and my treadle count (4 per drafting length for a theoretical twists per inch of 3 (4 treadles x 9 turns per treadle) divided by 12 inches = 3 twists per inch of yarn). I used a short backward draw (my default) on a Lendrum Single Treadle with a 9:1 whorl. I spun a basic beginner/intermediate yarn, the kind of yarn a spinner might make during a session of casual spinning, after which she decides she likes what she's done and would like to make more for a project.
This is my sample sheet. If you click on the photo, you should be able to read my calculations, so I won't relist them. In general, I aimed for 3 Twists Per Inch (TPI) in my yarns; in most cases, I was out by .25 to less than .5 turns per inch in the finished yarns. I used Mabel Ross's formulae for calculating TPI in yarns, because hers is the most common way to measure TPI in spinning programmes and literature. Mabel's theories make sense on paper, but what I discovered was a bit of a surprise-although I'm an experienced spinner and do a lot of calculations on hand spun yarn, no matter how carefully I worked, my results did not always line up with the given equations. They were closer when I was spinning a more or less balanced yarn, but when I began playing with the amount of twist, all bets were off, even using Ms. Ross's calculations for fancy yarns. Not only that, TPI, like so many other things in spinning, was affected by finishing (in this case, a hot soapy wash and hot rinses), shifting the TPI from .25 to .75 turns per inch. While a .25 variation in TPI might not be noticeable in a yarn with more twist, it's certainly noticeable in such low twist yarns; a .75 variation in TPI is a large difference in these types of yarns.
Hmm. Using TPI as a measurement system was not working out well for me, which could be for several reasons: a) I wasn't careful enough when spinning and measuring (I did my best and measured each yarn 4 times in 4 different sections); b) I don't know how to measure yarns (I read the books and practiced, practiced, practiced.); c) TPI measurements work in theory, but may not work as well in real life.
Next came Wraps per Inch (WPI). In the upper left hand corner of the above photograph, you can see my standard method for measuring WPI-I wind the yarn around the one inch segment of an embroidery thread holder. (Actually, I wind the card to wrap the yarn in order to maintain twist consistency.) I measured the yarns again, using a Spinner's Control Card and the iSpinToolkit on my iPad. (That's a tricky one: much as I love this app, if you load it onto an iPad mini instead of an iPod or iPhone, the scale changes. The TPI gauge becomes a 2 inch x 2 inch square, rather than a 1 X 1, so you have to divide everything by 2. Not only that, the instructions for calculating TPI from your measurements are incorrect, or at least, open to interpretation. Most spinners will catch the shift in scale, but may not catch it on the WPI gauge where the WPI count at least doubles, i.e., the 7 WPI I wound on a card became a 14 WPI using the app, which would be a major problem if you didn't know or didn't catch the change. Just to throw a bigger wrench into the system, the Angle of Twist calculator on the app is accurate.) The WPI count between the cards and the Spinner's Control tool were very close for the balanced yarns, but way off for the overplied sample, with my wrapping giving me a count of 8 WPI and the tool a count of 12 WPI. (Mr. DD points out that holding the yarns "taut" as instructed in the control kit is open to interpretation, because he tended to stretch the yarns out more firmly than I did, which would affect a lively, overtwisted yarn more than a balanced yarn.) So, I either improved my accuracy in measuring yarns with WPI or measuring WPI is a more consistent way to measure yarn size, although it doesn't help for measuring how much twist is in a given yarn, which calculating TPI is designed to do.
For my second attempt at measuring yarn twist, I turned to Angle of Twist (AofT). The theory here is simple: if you line those yarns up against a protractor or an angle guide so that the angle in the plies (or the tracers in the singles) align with the angle on your guide, you'll have the AofT which tells you how much twist you have in a given yarn. You can't compare yarn size with this measurement, because yarns of varying sizes can have the same AofT, but you can judge relative firmness or softness in your yarns. I used a clear plastic protractor and the Angle of Twist guide on my iSpin app.
This calculation is where my measurement skills truly shone. Either that, or measuring AofT is an accurate guide to yarn twist, because I was just about bang on every time I measured my samples. My measurements using the protractor were off by between .1 and .4 of a degree compared to the measurements on the app. (Mr. DD's yarn measurements using these tools were dead on.) Yay, me. All this ciphering had done me some good.
Well, perhaps. Perhaps several decades of calculating yarn measurements had been improved by a day's worth of careful calculations. What I suspect is more likely-I'm open to debate on this one and will do further testing-is that TPI, which is used so much in the spinning world to compare yarns, in reality, may not be a very reliable method of measuring yarn twist. It has its uses; like WPI, your practiced TPI counts are likely highly accurate when measuring your own yarns; however, if you or I are measuring and comparing one another's yarns, our calculations may vary widely and not necessarily because one of us doesn't know how to do math. The theory behind it is great and is useful when you are spinning your yarns, but as a system of measuring those yarns, a combination of WPI and AofT calculations might allow us to compare our yarns more accurately.
Spinners look for a common language to compare our yarns so that we can better understand how other spinners (and commercial mills) design and spin their yarns and how we can control and improve our our work. It may not be that one spinner is correct and the other is wrong in the way we measure yarns. Like language, there are nuances, subtle differences in how an individual speaks about the yarns she makes. The language of yarn and the differences among us are affected by simple things such as the way we hold our wrists when spinning, how hard we push on the treadles, the tiny shifts in drafting length we make as we spin and spin and spin. Our yarn measurements may change with the degree of pressure in our winding or the way we lay our yarns under a tool or even with what we expect to find as we do those measurements. This doesn't mean that we should abandon our calculations and our measuring tools. It may just mean that we need to learn to sing and dance with our yarns differently.