How I came up with the numbers I used in The Fleece & Fiber Sourcebook, part 1

I've been promising, or threatening, to write a post about how I came up with the numbers used to describe the fibers in The Fleece & Fiber Sourcebookyou know, the parts in the boxes, where the text talks about fiber diameters, staple lengths, fleece weights, and the like.

The short answer is that . . . well, there isn't a short answer. The shortest is that I didn't just copy numbers from somewhere else. Instead, I did research, drew on almost forty years of experience looking at and handling wool, and came up with numbers that I thought would best represent what a fiber person (for example, me) could expect to find.

Two decisions, one philosophical and one practical, set the foundation for my work with the numbers.

Philosophically, I wanted the data we provided to reflect what fiber folk were likely to hold in their hands: in other words, to give a reasonable ballpark idea of the range of fibers an animal, or breed, is probably growing.

From the practical perspective, I wanted a consistent approach to underlie all the sets of numbers.

Co-author Carol Ekarius and I had already spent months deciding what would be on our list of animals to cover.

The first thought that arises for anyone engaged in such a quest is to use the numbers published by breed associations. Yet those aren't available for all breeds and not all types of animals have breed associations. In addition, those numbers may reflect a particular group of people's ideal for judging animals in the show ring, not what's showing up on the shearing floor.

What comes next is wondering how people who have written down numbers before have decided what to use—but that lasts only a moment, because in almost all cases the back stories can't be discovered. A reasonable approach would be to choose an ostensibly reliable source and copy its numbers. I've done this in the past, as a result of personal curiosity and for my own notebooks, and it takes a long time.

Yet this time I was responsible to more than my personal curiosity—or, rather, to new levels of that curiosity as well as to a potential community of fellow fiber-users. So I moved to a new level that involved gathering as many numbers as possible for each type of fiber from a wide variety of sources, and then taking a look at them to see if I could discern patterns or irregularities.

To demonstrate my process, I'm going to use four sheep breeds that presented radically different problems in deciding what numbers to use:

  • a very consistent breed (Cormo)
  • a breed with a lot of variety (Romney)*
  • two breeds with almost no data (Santa Cruz and Hog Island)


* If I'm feeling brave when I write up the "a lot of variety" section, I'll mention the Cheviots again. . . . Does it indicate anything that, when I went to link to a blog post about the Cheviots, I could remember the EXACT MONTH AND YEAR when I had a serious tussle with their identities and data? I have a good memory, but for things like "when did I write that specific post?" I generally need to refer to my notes. Not in this case.


The numbers part of writing The Fleece & Fiber Sourcebook operated as a separate sub-project and had its own dedicated working spaces, including a physical folder:


It was about 1.5 inches (4 cm) thick. Inside were sections with pockets:


It also willingly held a few extra manila envelopes of papers.

I happened across this organizer while I was buying yet another dozen cardboard file boxes to hold fiber samples. I bought it on a whim, feeling extravagant because I had no precisely defined use for it. It became a reliable sidekick. Although the data it held was partnered with a lot of computer files, my thinking processes took place with the help of the papers it protected.

As I mentioned, I began by simply gathering data presented by other people. I looked at the Oklahoma State University site and at Wikipedia, of course, in part because many fibers are listed and it's nice to start a search with success (or to be warned that the digging will need to be deep). It was interesting to discover later what the sources of these sites' data were—when I located matching material elsewhere that appeared to predate the compilations. I was able to perceive this cross-linking between sources (print and web) from time to time throughout my research, and it helped me evaluate and weight my results.

Then I consulted as many breed and trade associations as I could locate, performed multiple web searches, and prowled through a couple of shelves full of books. Repeatedly.

When I had exhausted at least myself, if not the options (although I worked to plumb those as deeply as I could), I assembled in a spreadsheet the data I had found for each type of animal or breed of sheep.


Example 1:


Cormo is a relatively modern sheep breed developed with strictly defined performance standards, including for the quality of the wool. Individual animals that don't meet those requirements are culled. You'd think I could have almost instantaneously processed this breed through the numbers-cycle. While it was easy relative to other fibers, it shows that none of my decisions worked by cut-and- paste.

Sometimes I obtained information in imperial designations, sometimes metric, sometimes the Bradford or USDA numbers. (These two systems use the same notation system, although they are not completely interchangeable.) I started by putting whatever information I had on one sheet of paper (well, sometimes, as for the Romney, two sheets of paper).

Here's my Cormo list, in its neatly presented spreadsheet form:


Because I ended up looking for regional variations, I coded the column just to the right of my source indicators for the potential geographic bias of the data, if I could perceive one. (1-US, 2-UK, 3-NZ, 4-AU.) If I wasn't sure, I left the column blank. (Fournier & Fournier sometimes got coded as 3-NZ—when the data matched what I found in a New Zealand breeders' association. Sometimes I could tell where Wikipedia's information had been drawn from. In this case, the Oklahoma site referred specifically to Australian sources.)

While Cormo was one of the simplest breeds to come to conclusions about, you'll note discrepancies in the collected numbers.

In staple length, the two sources I found said 2.5 to 4 inches OR 4 to 5 inches. Well, 4 inches seemed like a safe place to land, but there will always be some variety in a natural item like wool. I knew from experience that not every Cormo fleece is exactly 4 inches long.

Staple length can be defined either as "how much wool can these sheep grow in a year?" or as "how long was the wool that the shearer clipped off?" They're not the same. Which were people talking about?

Suspending judgment temporarily, I simply moved to other parts of the summary to see what I could learn.

In fiber diameter, I found additional intriguing oddities. Initially, the numbers looked pretty consistent at 17 to 23 microns, with 21 to 23 microns coming from In Sheep's Clothing (Fournier & Fournier), possibly a reflection of the authors' New Zealand origins. (The breed developed in Australia, but there might be more focused goals among New Zealand breeders. Or not. This was part of my discovery path.)

Turning to ASI, which is the American Sheep Industry Association, I found an even more arresting set of numbers. These were at cross-purposes to each other. This source specified both 17 to 23 microns AND 46s to 56s USDA grades. The micron equivalents of USDA 46s to 56s are 26.4 to 32.7. The site did helpfully specify that it was looking at American Cormo, which might mean it was recording information on a regional variation, even though with this breed the standards appeared to be both strict and internationally consistent.

Fournier & Fournier, with their 21 to 23 microns, in addition specified 64s to 58s. They didn't say whether this was Bradford or USDA, but in either case a ballpark equivalency would be 21 to 27 microns. The grades corresponding to 21 to 23 microns would instead be roughly 64s to 62s, a much narrower span.

I'm skipping lightly here over a discussion of how Bradford numbers differ from USDA grades. We did talk about that in the book. By the way, I constructed the chart comparing fiber counts and USDA grades that appears on pages 12 and 13 of The Fleece & Fiber Sourcebook to help myself keep track of all this stuff.

Now, without having resolved anything, I turned to fleece weights. As an initial observation, rams and ewes tend to produce different amounts; rams grow heavier fleeces. Yet a lot more ewes are kept and shorn, so sometimes fleece-weight numbers ignore the rams. Like staple lengths, fleece weights are subject to a lot of interpretation, because the parameters aren't specified. In addition to "ram or ewe?" there's "a full year's maximum growth?" and "skirted, or not?"

The general assumption is that a fleece weight will be grease, not clean; a full year's growth; from a ewe; probably lightly skirted.

But you never know whether that is the case for a particular set of numbers unless it's spelled out.

Where my chart says (e), that means the source specified that this was the weight of ewes' fleeces. (Similarly, some of my charts have both (r) and (e) measurements.)

The Cormo Sheep Conservation Registry liked 12 pounds as a nice, single number, presumably an average. Fournier and Fournier were in the same vicinity, with 9 to 12 pounds. ASI thought fleeces from this breed would be a good deal lighter, 5 to 8 pounds, but they also specified that they were talking about ewes.

When I did my research on Cormos, I did not find micron counts or fleece weights on the Cormo Sheep Conservation Registry website, which is now listing 21 to 23 microns and 5.5 to 12 pounds.

Okay, what to do with all these flying numbers?

At this point, I began to draw pictures.

When I first felt backed into one of these corners, I was on a retreat in Salida, Colorado. This was fortunate, because my retreat times gave me opportunities to stick with one thorny issue or another until I had resolved it, something that wasn't anywhere near as easy when I was home and juggling writing tasks with regular duties and interruptions.

I remember the morning I stared at a sheet of statistics that were not coalescing. I felt compelled to confront the problem with a pencil and some graph paper. I took a brain-clearing walk to the office supplies store and splurged on a spatious pad of quadrille paper, 11 x 17 inches of open territory on each sheet. Back at the cottage, I wrote reference numbers across the long side of one sheet and then sketched where all my different sources thought a particular breed's wool should be (I may have started with the Romneys).

This turned out to be a breakthrough. During my retreat time, I hand-wrote a number of these sheets and refined my system. When I got back to my home computer (and its printer), I made up an Illustrator file with the key across the top and lots of guidelines, like my quadrille paper, in the body of my form. I printed out blanks and used them the same way that I had the big sheets. With pencil. These got tucked into my blue pocket file, either alphabetically by breed or, when I was looking for patterns in particular groups, in clusters by family or fiber type.


The top row of numbers represents micron counts, in crisp, even numbers. Next comes the Bradford scale, and below that the micron counts broken into fragments (with standard deviations) assigned to Bradford-like numbers when the USDA grades were established. Below that, there are the traditional fine/medium/coarse/very coarse designations, and the bottom row relates all the other measurement methods to the old blood system.

What I ended up with for Cormo, as my final numbers to go in the book's box of data:

  • Staple lengths: 3.25 to 5 inches
  • Fiber diameters: 17 to 23 microns (in the realm of spinning counts 62s to 80s)
  • Fleece weights: 5 to 12 pounds

I'm sure some Cormo fleeces are as short as 2.5 inches, but the wonkiness in the ASI wool grades made me mistrust that low end. Of the Cormo wool I've seen, the 4- to 5-inch range seems typical, although some has been shorter.

It seems clear that 21 to 23 microns is where the breeders would like the wool to be. It also seems likely that some may be as fine as 17 microns.

Because of the difficulty of confirming Bradford versus USDA throughout the entire inquiry, and because many people are familiar with those methods of describing fiber diameters, we supplemented the micron counts for fiber diameter with what we called spinning counts, meant to communicate in terms similar to those of the two closely related older systems.

For this breed, one developed at a time when micrometer measurements were coming into fashion and one that is defined in part in terms of the micron counts of its wool growth, I gave more weight to the ranges in microns than to the USDA-Bradford-style numbers that were causing problems. In order to get our "spinning counts," I translated from the micron measurements, coming up with 62s for the 23-micron end of the range and 80s for the 17-micron end. It seems pretty clear that most of the wool will be 21 to 23 microns, or 64s to 62s, but we couldn't write a whole essay like this about every breed.

I settled on a range of 5 to 12 pounds to take into account the span from what was probably a light ewe fleece to what was likely a heavy ram fleece.

Wool is a natural, not manufactured, material. It will always have variability—more than anyone coming newly to the topic of studying it can begin to imagine. Getting more precise numbers would require a dedicated research project for each breed (with an extensive budget for communication with breeders, likely including travel, as well as sampling and analysis). The end results would not serve our intended purpose any better than what I'd done.


Having wrestled a clutter of numbers to a ground of my own defining, I would let myself spin some samples, as a reminder of what it was all about: a person, at a wheel, with some fiber, enjoying the process of making yarn.

And that's enough for one day. I'll continue later.

090326 snow and ghost spinning lights 010

Spinning photo taken on a writing/research/spinning retreat in the mountains of Colorado, March 2009. Photo by writing friend Judy Fort Brenneman.


Information and new sources continue to appear. Here are a couple of items that would have fed into my research, except that they appeared after I had to call it quits and give the manuscript to the publisher. (We tweaked until the last minute, but couldn't continue the fundamental heavy lifting for that long.) First there's an article with great quotes from Ian Downie, who developed the Cormo breed. Second, a new registry was established in 2009, also too late for inclusion.

The new Cormo Breeders Coalition has this to say about the wool: "Sample from mid-side 1723 micron. Consistent wool with 90% of wool within a two micron range. Staple length 3.5” to 5.5”. Dense soft wool. Fleece weight mature ewe 5–8 lbs." Add this set of numbers to my list.

There's always more to be discovered! Sometimes those discoveries will result in corrections to previous conclusions. In this case, I read that and said, "So far, so good for my conclusions on that breed."


4 thoughts on “How I came up with the numbers I used in The Fleece & Fiber Sourcebook, part 1”

  1. I couldn’t imagine even where to start with compiling all this information and knowledge, and it gives me such joy to have a book in which it’s all been done with such care and love!

  2. Now this is as fascinating as the book… I didn’t think it could be possible (threat? promise? well worth the effort)

    You know how much I love your Shetland chapter but I am dipping into the others – there are some breeds I haven’t played with yet and thanks to you they are baaaing to me.

  3. I’m really glad you’re enjoying reading about this. I’m working on the next segment, and hope I have time to finish it this week.

    Cathy, the Shetlands took an enormous amount of work, and I’m far from done with my research on them. LOTS of history and opinions about what they have been and are, and how those connect to each other.

    It’s important to be clear that I’m not setting or even having opinions on standards for breeds: what I am doing is bringing together, and summarizing, information from a lot of sources. It’s a practical and descriptive exercise, rather than a prescriptive one! I’m fascinated by all of the factors at play in these questions about what the wool is like.

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