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What are WPI and why?

We've had LOT'S of people quietly <very quietly VBG>ask us how to use a WPI Gauge and what they'd do with one.

Well, the first thing you should know is that you don't need one of our gauges -- using a ruler works almost as well -- some people mark an inch off on a pencil and use that. But if you enjoy using pretty, good-feeling tools -- well then, you MUST have a Hatchtown gauge! <BG>

"WPI" stands for Wraps Per Inch. You measure them by wrapping your yarn around an inch of something. Then you simply count the number of "wraps" it took to fill the inch. The only "techniques", so to speak, are to keep an even 'almost no' tension while you're wrapping....and to not pack the wraps together too tightly -- you want them to lay politely beside one another so that they just hide the surface of whatever you're wrapping them on.

• Weavers use WPI to pre-determine how many EPI (Ends per Inch) they'll need for a warp.
  • To calculate the warp's EPI for a weft-surfaced plain weave like for a tapestry, simply wrap the weft and warp yarns together -- the two yarns laying side by side at each wrap -- counting the number of wraps the two yarns made as a pair gives you a good starting EPI.
  • Weaver's reference books have complex formulas with which you can calculate EPI for complicated, repeating patterns -- using the WPI of the weft and warp threads.
• WPI gives spinners a standardized way to communicate to one another about the fineness or thickness of their latest output. Who's really going to be impressed when one spinner says that her yarn is VERY VERY FINE (meaning it's probably MUCH finer than ANYTHING other spinners are capable of!). WOW them with WPI! <VBG>
• Knitters use WPI to figure "adjustments" when not using the same weight commercial yarn suggested by a pattern. Esther Bozak, a good Hatchtown friend has compiled an extensive chart that gives the specifications of the different sized yarns -- WPI is (are?) cited prominently. She originally posted the chart on the KnitList; you can link over to it on the Fiber Link website == Esther Bozak's Amazing Yarn Chart <BG> You'll have to use your browser's "BACK" button to return here.
• Kumihimo braiders don't talk WPI much, but maybe they should. If 64 strands of silk on each of 8 bobbins using a particular braiding method results in a 3/8" diameter braid.
  • How many fewer strands of 20/2 cotton should be used to get that same 3/8" diameter??
  • What will be the diameter of the braid using those same 64 x 8 strands but in the cotton??

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