What's the Grist?

How we measure yarn based on weight, not wraps

By: Amanda Kievet

“I’d like a Worsted weight yarn,” said a sheep farmer dropping off their Shetland fleece at the mill for processing recently. It’s a reasonable request, but it's just where the confusion begins. Familiar measurements we all know from shopping at yarn stores — DK, Aran, Lace —  don’t work at a custom processing mill.

Wraps per inch (WPI) based measurements like those referenced above best describe the diameter (thickness or thinness) of an individual strand of yarn. As the name suggests, they’re based on measuring the number of times the yarn can be wrapped around a ruler to fill one inch. You can see the full list of WPI-based yarn sizes here on Ravelry. The reason WPI based measurements don’t work at our mill is that they are impossible to calculate before the yarn is actually spun.

Yarn wrapped around a 1" measurement tool

Finished yarn wrapped around a 1" measurement tool to determine final number of wraps per inch

During processing, we put a lot of tension on the fiber as it is picked, carded, drafted and spun tightly onto bobbins. After the spin, when we take the yarn off the bobbins and rinse it, the fibers are finally able to “bloom”, or puff up and release the tension we put on them. If we were to measure the WPI of yarn before the final rinse and again after it’s rinsed and dried, the difference can be dramatic. So we don’t know what the final WPI measurement of the yarn we’re making is until it’s already too late to change it.

Instead, we work in a unit called “grist”: the number of yards per pound of yarn. We use this measurement because it is measurable at all stages of the process.

At JFM, we spin yarn with grist between 1100 and 500 yards per pound. We call yarns on the higher end “light” and on the lower end “medium”. For the same fleece, the higher the grist, the thinner the strand of yarn; the lower the grist, the thicker the strand. But two different fleeces spun at the same grist often produce two very different-looking yarns with wildly different WPI measurements. This is because WPI is affected by a whole slew of other factors: amount of crimp, individual fiber thickness, staple length, amount of twist, etc.

Left: Teeswater blended with Falkland spun at 730 yards per pound, Right: 100% Corriedale spun at 1050 yards per pound

Left: Teeswater blended with Falkland spun at 730 yards per pound = "sport weight", Right: 100% Corriedale spun at 1050 yards per pound = "worsted weight". Despite being much thinner/finer/higher-WPI, the Teeswater was spun at a "medium" grist and the Corriedale at a very "light" grist.

Example 1: Breeds with low crimp

If you came in with a straighter-fiber fleece like Cotswold, Gotland or Teeswater and wanted a “Sport weight” or “DK weight” yarn, we would expect that would fall well into our “medium” range due to the lack of crimp. These types of fleeces make wonderful higher WPI yarns (Fingering, Sport, or possibly DK), but if we tried to yield a lower WPI yarn (Worsted or Aran weight), we would have to spin at such a heavy grist that we would end up with rope and so would highly advise you against this.

4oz skein of Teeswater blended with Falkland spun at 730 yards per pound

Teeswater wool blended with Falkland to add a little more crimp, spun at 730 yards per pound/182 yards per 4oz skein. Finished wpi category: sport (12 wpi).

Example 2: Breeds with high crimp

If you had a fine fiber fleece with a lot of crimp — Merino, Corriedale, Cormo — and you wanted a “Sport weight” or “DK weight” yarn, we would have to spin at the high end of our grist range in the “light” category, and we likely would not be able to achieve such a high WPI measurement even still. Because of the crimp, these fibers bloom so much that it’s difficult to spin anything finer than a DK weight yarn within our max of 1100 yards per pound range. These fleeces yield light and airy yarn which tends to fall in the Worsted or Aran weight range. If spun three ply “medium” the yarn might even cross into Bulky.

4oz skein of 100% Corriedale spun at 1050 yards per pound

100% Corriedale wool spun at 1050 yards per pound/262 yards per 4oz skein. Finished wpi category: worsted (9 wpi).

These two examples illustrate the extreme ends of the spectrum and many fleeces and fiber combinations fall somewhere in the middle. When we say we do “custom processing”, it truly is custom. We take the time to assess your individual fleece/s along with your goals to determine what kind of yarn it wants to be: What grist will do it the most justice?  How much twist should it have? Would blending a little [straighter/more lustrous | crimpier] fiber yield the result you’re looking for? We can advise you based on the unique characteristics of your fiber and with your specific goals in mind what type of yarn will allow it to shine.

For more information about custom processing at our mill and to see the current prices, visit our processing page.


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