Tuesday, December 08, 2015


As a spinner, I use wraps per inch (wpi) often. If I do a good job of measuring wpi, then the square of wpi is the grist in yards per pound. And the twist factor times times wpi equals required twist in tpi.

It works.  Mostly it is within 10% of the actual grist, and with corrections for fiber and construction, wpi can measure grist to within 2%, which is better than a yarn balance.

To measure wpi so that it indicates grist, you need a wpi gauge, you need to pack to refusal, and you need to practice.  You need to take various kinds of yarns with known grists, and practice doing wpi, until you get the correct grist, time after time.  It is a skill.

So, when a knitter says a yarn is 18 wpi, I figure the grist is 324 ypp (e.g., 18x18) -- that is like rope. Then, she gives the yarn band info of 175 yard per 2 oz. -- or 1,400 yards per pound. That is sock or fingering yarn. When I measure the wpi of that yarn, I get 37 wpi.  That tells me, and other spinners, the grist.

Packing the yarn to refusal gives a definite measure that can be made anywhere by anyone. Packing the yarn loosely so that a 1,400 ypp yarn so that it yields a wpi of 18 is not a repeatable measure of -- anything.  This approach is as much a measure of twist as of grist.  With this approach, high twist yarns will seem to have much lower grist than yarns with the same grist, but less twist - and vice  versa.

If you pack to refusal, then worsted and woolen yarns of the same grist will have the same wpi.  If you use the loose knitter's wpi, then worsted and woolen yarns of the same grist will have very different wpi.  If you pack to refusal then yarns of the same grist but different twist will have the same wpi. If you use the loose knitter's wpi, then yarns that are the same grist, but which have different twist will have different wpi.  This is silly.  What really counts to a knitter is the length and weight of the yarn.  These should be described by the wpi.  Twist of the yarn is less important.

In my world wpi and grist are related thusly:

wpi       grist (ypp)   spin count           notes

 22         484                                        Aran Yarn (traditionally was 10-ply of 10 count singles)
 24                             1
 26         676
 28         840                                        Worsted Yarn (traditionally was 6-ply of 10 count singles)
 30         900
 32         1,000                                     Gansey  Yarn ( 5-ply of 10 count singles)
 33         1,100                                     DK weight yarns
 34         1,120           2                        
 38         1,443                                    Common grist for commercial sock yarns e.g., Wooly West
 40         1,650           3                      My 6-strand sock yarn
 42         1,800                                   Single cut woolen singles         
 44         1935                                    Fingering Yarn
 48         2,303                                   Jumper Weight/ Spindrift weight 2-ply
 53         2,800          5                        
 60         3,600                                    2-cut woolen singles @ 9 tpi
 60         3,733          7                        Traditional 6-ply sock yarn from 40 count singles
 64         4,100                                     Modern lace weight
 75         5,600          10s                    Singles for warp/ 9-10 tpi  & woolen singles for weft @ 12 tpi
 80         6,700          13                      Traditional 3-ply Shetland lace plied up from 40 count singles
 105       11,200        20s                    Worsted singles that I use for my sock yarn @ 14 tpi
 120       14,400                                   8- cut woolen singles / 18 tpi
 130       16,800        30s                     Worsted singles @ 17 tpi
 136       18,000                                   10-cut woolen singles / 20 tpi
 142       20,200                                  2-ply from 80s  
 150       22,400       40s                     Traditional grist for singles used for best sock yarn/ 17 -20 tpi
 182       33,600       60s                     Traditional commercial  "fines" / 22- 24 tpi
 210       44,800       80s                     Traditional best commercial "fines"  /24 - 27 tpi

A defined ratio between wpi and grist make working with yarn easier.  In fact, I would go so far as to say that the textile industry was likely more important to defining various units of measure than the size of the king's foot or finger.
Twist per inch numbers reflect the firmer yarns that I am spinning since starting to spin warp. Before, my 40 count singles were only 17 tpi. These higher tpi were allowed by my move  from 25 mm to  ~50 mm flier/bobbin whorls.

And, it is all hand spinning.  Everything above is plus or minus 10%.  I calculate grist by winding hanks of 560 yards and weighing them on a kitchen scale to the nearest gram.  In the past, I used a jeweler's scale to weigh fine spinning.  Now I just weigh fine hanks 4 at a time and calculate the grist on the basis of  grams per 2,240 yards.

ETA - It is worth noting that plying takes up about 10% of the length of  the starting singles.  Thus, if one starts with 5 hanks of 10s, then one gets just over 500 yards of gansey yarn, and the grist of the 5-ply gansey yarn is is a bit more than the 5 times the grist of the singles.  This small change in grist cannot often be measured by wpi.

No comments: