How long would the yarn supn from a single sheep's wool be?
November 4, 2011 2:10 PM   Subscribe

This is a Fermi Question, I only need an approximate answer: How long would the yarn spun from a single sheep's wool be? Is 2 miles reasonable? What's a good lower bound?

My first instinct is that two miles is way too long, but here's how I got that initial guess:

I found a standard type of wool yarn that is priced at $14/ 200g or 220 yards, so, the yarn must be about 1g/yard
I also looked up the average annual yield of wool from a sheep: "In 2007, the average sheep in the U.S. produced 7.3 lbs. of grease wool." -- reliable website

There are 1760 yards in a mile, and 453 grams in a pound.
Thus, 7lbs*450g/lb= 3150 grams of wool = 3150 yards of wool = approximately two miles of wool yarn...

but this number just doesn't seem right! Where am I going wrong and what's a better estimate for the approximate length of wool yarn that would be produced by a sheep in a year.

Any help appreciated! Thanks!
posted by ch3cooh to Science & Nature (10 answers total) 1 user marked this as a favorite
According to this, you're going to want to cut 50% of the weight off the top due to loss from scouring and spinning.
posted by Jacob G at 2:21 PM on November 4, 2011

One problem is that, after the sheep is sheared, as the wool is processed for spinning it loses a lot of weight. First, it's generally "skirted" meaning the dirty, matted outer portions are removed. Then, when it's washed it sheds a lot of dirt, debris, and oils. Then, many parts of the wool are removed because they're not really suitable for spinning - the "short pieces" are bits where the shearer had to go back and re-cut, and the fibers are too short for spinning.

I'm having a hard time finding out the average weight of a bag of fleece from one single sheep after it has been washed an prepared, but I know it's out there somewhere.
posted by muddgirl at 2:23 PM on November 4, 2011

A few things to consider: 7.3 lbs of grease wool is reasonable, but that only yields about 5 lbs once it has been washed. You'll also lose a little more when you comb it.

Secondly, the answer varies greatly depending on how thick you spin your yarn. Theoretically, you could spin it very, very thickly and end up with quite a short length (so I'm not sure how to calculate a reasonable lower bound). Wool was traditionally graded by spinning count, which is a estimate of how many hanks (560-yards) you can spin from a pound. Roughly, Sixty is a middle of the road wool, so you could theoretically spin somewhere around 100 miles of yarn from one fleece if it was relatively clean and quite fine.
posted by ssg at 2:25 PM on November 4, 2011 [2 favorites]

You'll have to specify what weight of yarn you're using. "Standard" is typically worsted weight, while a fingering weight would be much thinner, and laceweight thinner still.

Cascade 220 is a pretty standard worsted yarn, with 220 yards per 100 grams. Cascade 128 has the same fiber content and the same weight (100 grams) but is thicker, thus producing 128 yards. Lana Grande is 87 yards.
posted by Madamina at 2:30 PM on November 4, 2011

Yarn comes in many different thicknesses, so that is really going to affect your answer. Laceweight yarn is going to result in a much different result than worsted weight.

Now, I'm not a spinning expert, but I do knit and have spent a fair bit of time around yarn. As I understand it, spinning is not anywhere near a zero-sum game. If you start with a raw fleece, it is going to have, in addition to useable wool, quite a lot of excess dirt and vegetable matter, as well as a significant amount of lanolin. While you can certainly find yarns that leave in the lanolin, a large portion of the yarn on the market does not. The lanolin is what they're referring to by "grease wool". Now, this is all still in the general cleaning process.

The next step is carding the wool, effectively combing it until it resembles these long fluffy tufts. You will lose fiber content during this process, because invariably, strands will be too short to use, long ones will break in the process, or just not work in properly. You'll then encounter similar fiber loss during the spinning process.

My guess is that if you have the world's most pampered sheep and used the most meticulous shearing/spinning process known to man, you'd probably be able to preserve more of the wool, but I think you should be thinking of wool processing as similar to raw cotton processing. You're not just peeling finished sweaters right off the sheep. They're dirty, dirty animals, and spinning is far from an exact science.
posted by Diagonalize at 2:32 PM on November 4, 2011 [2 favorites]

Contact your local ag extension and ask to be put in touch with your local/area/regional sheep-to-shawl team.
posted by MonkeyToes at 2:50 PM on November 4, 2011 [1 favorite]

"Grease wool" means wool that hasn't been cleaned yet. There's usually a fair amount of dirt, and there's a lot of lanolin, a wax that the sheep secrete along with the hairs.

When the wool is cleaned, a substantial proportion of the weight goes away with the detergent. I have a vague memory that it's more than half, but don't quote me.
posted by Chocolate Pickle at 2:57 PM on November 4, 2011

This search for the phrase "each sheep yields" has a few useful facts about the different weights from different sheep breeds (varies from 2 lbs to 15 lbs per sheep, depending on breed, how the animals are grazed, temps of their habitat, etc) and different amounts of shrinkage the fleeces undergo in cleaning (from 12.5% shrinkage to 50% shrinkage or greater).

Most significant for your purposes, a quote from the Montreal Gazette (Dec 4 1978) saying that 8 lbs grease wool = 4 lbs cleaned wool on average.
posted by LobsterMitten at 4:46 PM on November 4, 2011

I have spun yarn from a single sheep's fleece. From just about 6 lbs of grease fleece from a Romney sheep, I spun 3200 yards of three-ply sport-weight yarn. Of course, since that was 3-ply, your answer could be that I spun 9600 yards of yarn -- depending on how you define "yarn." I've also spun yarn that was so light and so fine that I could get 4000 yards from a pound of clean fleece.

Just for comparison's sake, a medium-sized plain adult sweater would take about 1500-1800 yards of worsted-weight yarn.
posted by KathrynT at 9:21 PM on November 4, 2011 [2 favorites]

These answers are amazing and exactly what I needed to know! Thank you so much everyone!
posted by ch3cooh at 12:50 PM on November 5, 2011

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