I once bought a Rambouillet fleece from a woman in New Mexico who was trying to refine the breed to create the finest fleeces, better than the merino it was derived from. She had each one micron-count lab-tested and then she priced according to those results.
I decided if I were going to spring for one, I was going to get the best I could.
This is before I had a drum carder. I quickly realized my hand cards and my wrists and that wool were not a good match and sent it off to a mill to be commercially washed and machine-carded into roving for the fast-food version of handspinning: just sit at my wheel and go.
I even got sent a picture of the sheep! With its poetic name, Number 1243 or some such.
The mill said it did fine fleeces like merino. What it didn’t tell me when I made inquiries is that they hadn’t quite yet bought fur carders, which is what most superfine wools require. (They did a year later.)
They botched it. My beautiful, first-class fleece came back full of neps, the little rolled-up pills that are the nemesis of good sweaters everywhere–before the wool had even been made into yarn yet. Picking them out was a task that would never have ended.
I actually made a pair of soft slipper socks out of them, even so. I started a second and much larger project, but the could-have-beens and the visual interruptions of those pills got to me and I eventually abandoned it. From there, it sat for awhile till I donated most of the roving to the Boy Scout troop for stuffing in their shoes for comfortable feet on long hikes.
So yes, it’s true: loose neps sink WIPs.