Saturday, April 19, 2014

Twist and Grist

I have been accused of getting my twist numbers wrong.

That is unlikely.  I may have made a typo here or there, but over all, I am the one hand spinner that always knows his twist.   I use differential rotation speed (DRS) without slip to control twist insertion.  Once I install the whorls on the wheel, I know how much twist will be inserted.  If I want a thicker yarn, I do a more woolen preparation.  If I want a thinner yarn, I do a more worsted preparation, and thus I can get a range of yarns from particular whorl combination that inserts a specific twist.  However, I can always look at the whorls on my wheel and know how much twist is being inserted.

Thus, I have to know the twist for every yarn that I plan to make.  Once the whorls are (made and) installed -- the twist is set.  How fast I treadle does not affect inserted twist.  How fast I draft does not affect inserted twist.  Yarn build up on the bobbin does affect the effective diameter of the bobbins and hence rate of take up and hence twist.  However, this is a known factor that is predictable.

I know that when the whorls that produce 9 tpi are on the wheel, and I am spinning worsted I get 10s (5,600 ypp).  I have measured, and validated this hundreds of times.  I know that when the whorls that produce 17 tpi are on the wheel, I get 40s.  I have measured and validated this many times. I also have whorl combinations for 5s, 20s, 30s, 50s, 60s, 70s, and 80s that have been have measured and validated. Each allows me to produce a specific grist of worsted and a different, specific grist of woolen and intermediate grists of semi-woolen and semi-worsted.

If I want to sit down and just play with a fiber, then I am likely to set the wheel up as single-drive, bobbin lead (Irish Tension).  Most of my plying of hanks of  5-ply  gansey yarn or 10-ply Aran weight are done using the Ashford ST Jumbo flyer. Thus, every week, I do work with ST and IT fliers. With IT or ST my twist is as fallible as anyone's. However, most of my spinning is done with DRS because it is more productive and my twist more precise.    Spending a lot of time working with precise twist makes me a better spinner when I am using ST or IT.  Sock weight yarns with large numbers of plys are plied using DRS control of  the AA #1 flier. This holds twist to within a few percent. That limits my sock yarns to skeins of about 10 grams or about 80 yards.  Small skeins are my penalty for demanding precise twist in my 6-ply sock yarns.

On the other hand, my WPI measurments tend not to be consistent with several other authors.  I worked with yarns of known grist and practiced doing WPI until my measured WPI for 5,600 ypp (10s) was a consistent 75,  my measured WPI for 11,200 ypp  was just over a hundred, my WPI for shirting or hosiery yarns was 150, and etc. This seems different from other authors, but most do not write about spinning this fine. In every case, my WPI tests were done with worsted spun rather than woolen yarns., and this may explain some of the difference. However,  I always pack to refusal, because it provides more consistent results. At this time, I do not trust my WPI for woolen spun yarns.  It is likely off by 10 % when it should be accurate to 6%.  Thus, to get the grist of woolen yarns I weigh a measured length.

I think some authors do not pack to refusal, so their WPI and hence estimated grist and required twist are different from my numbers.  My numbers work - consistently.

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