Example: I see on Ravelry a gorgeous specimen of a Morning Surf Scarf, out of the Spunky fiber club's August 08 installment, Thermograph. So I decide I want to spin fat singles and make one just like it.
So I spin these.
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I've said it before: my idea of "fat" in spinning seems to be like an teenage girl's idea of "fat" in body weight.
Then, I cast on. Those singles seem awfully thin, so I cast on a lot of stitches. As a result, rather than a slender scarf, I get this.
Still, it's knitting up pretty nicely. But then I panic, because I've finished the first 2 oz of my 4-oz hank of fiber, and the scarf clearly isn't going to be long enough. So I quickly engineer a trade on Ravelry to get more of the fiber. At the same time, I spin the other 2 oz.
Clearly my concern about running out of fiber affected my spinning. Because while the first 2 oz yielded about 250 yards, the second 2 oz yielded about 500 yards. Even I can't call them "fat singles" any more.
And the scarf keeps groooowwwinggg.
Then, a little late in the game, I decide to test-block a swatch. Which grows from a little over 3 inches in length to 4.5 inches in length. Since I now have 5 feet of unblocked scarf, this gives rise to concern about the length of the finished product. I'm putting off the final blocking, in fact, because I'm scared.
Meanwhile, I have another 4 oz of Thermograph sitting there minding its own business. I decide to change gears and spin up a chunky yarn for this cowl. I decide to chain-ply it to preserve the colors. I need about 150 yards, and as I spin I keep thinking, "spin chunky! spin chunky!"
Well, I did.
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Here's what I got: under 50 yards of super-bulky 3-ply yarn.
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The thing is, I don't even care that I don't have enough for the cowl I wanted to make, because it may be my favorite yarn I've ever spun.