How about that?! Two weeks have flown by so I come back with a bit of Latin.
It’s been a wild August here on the mountain. Between my boys starting back to school on the 15th, 2 very large design projects I’m working on and all the swatching for proposals…..I’ve been wishing I had either a live-in assistant or that I could clone myself.
So I promised some substance for this post. Let’s take a quick look at WPI.
WPI – Wraps Per Inch. It’s a measurement used to tell the thickness or weight of a yarn. Spinners use this term a lot. It simply refers to the number of times that a particular yarn can be wrapped around an inch wide length. You don’t want to wrap the yarn tightly as it will distort the yarn and you want each strand of yarn to lay flat next to each other on your measure.
I had never heard of it until I joined Ravelry in 2008. Once I had though, I was amazed that it isn’t used as part of yarn labeling. It is a fairly accurate measurement and far less subjective than the categorizations of “worsted”, “dk”, “sport” and “fingering” etc that we see. Or the nifty little drawings with the number on a skein.
On that subject, I purchased this ball of yarn at Hobby Lobby ages ago. I liked it because it was a bright-colored light weight yarn. Imagine my surprise that it was labeled as a # 5 “bulky” weight yarn. Seriously?
Now sometimes with a really fluffy mohair kind of yarn that has a thin core I can see a yarn being labeled bulky. But there is no way this is a bulky yarn. Being I’m an experienced yarner, this sort of labeling mistake doesn’t bother me, but for your new yarn consumer or those less experienced this can be quite confusing. Particularly if you are looking to substitute a yarn.
It is easy to measure WPI in a store, especially on many of the larger commercial skeins. You can do it by laying the ruler at a 90 degree angle to the yarn wraps on the ball, or by slipping the ruler under one layer of wraps to see the number of wraps across an inch.
I’ll talk more about how this all helps when you want to substitute yarns. For now I challenge you to play with measuring WPI on your own. See if you start to get a feel for the WPI of various yarns.
Mamas2Hands 
Really great information here – thanks for sharing!!!
Great post, Andee. I really do prefer the numbering system in my country rather than the one from the US – it’s more detailed. Based on what our handful of manufacturers produced it has worked fine for many years as far as being able to trust what was on the label. However with a lot of our yarn produced overseas now, it get’s labeled as being one thing when really it’s either thicker or thinner as it was mostly intended for the US market.
I see many new people to Ravelry from my country try to work out what worsted “really is”. We tell them what to look for locally, but that they’ll have to do a swatch because worsted is such a loose term, whereas here we are used to dealing with a more exact product. 🙂
WPI is a useful tool, especially on unknown yarns. It can be just as unexact as other methods though, unless the same tension is used to wrap the yarn! LOL.
True about the tension being key to accuracy, still…I do prefer it over the seeming randomness of many of the other methods of measure.
Swatching is always important though, differing fiber content, tightness of twist and even the color dye used can all be factors in how a yarn works up. Probably the real reason I’m a designer…I like to make the yarn fit my idea, instead of making a pattern fit a yarn. ;o)