There are two different ways to come out even when plying.  I'll explain both methods to you. In the first method, you will need a scale to weigh the bobbins on, preferably a triple balance gram scale or a very accurate postage scale that weighs in hundredths of ounces. One thing that I have done is weighed all my bobbins (with a leader attached) on a gram scale and marked the grams they weigh when empty on each bobbin.  You will be amazed that the weight of each bobbin will vary by a few grams.    Then when spinning when I think the bobbin is full enough with singles I weigh it again and subtract the weight of the bobbin to find the actual weight of the yarn. .  Then I spin the rest of the bobbins so the have the same amount of yarn on them when weighed after subtracting  the weight of the bobbin.  Or another way to come out even in plying is to weigh the fiber for each bobbin first.  Right now I'm spinning Vicuna and will put 14 grams or a half ounce on each bobbin and then ply the two singles together.  With either of these ways I usually come out with only 2-3 yards being left on a bobbin. 

The second method involves no weighing of the yarn or bobbins.  You will positively come out with no leftover yarn by this method.  First you use a ball winder or a nostepinne to take your singles off the bobbin, you then have a center pull ball.  With the center pull ball, take both ends ,the outside end and the inside end both ends and ply those two together till you have reached the center and end of the yarn.  If you wish a 3 ply yarn over a two ply yarn, then just use the inside yarn end and do a Navajo ply, which is no more than doing a single crochet chain with your hands and making very big loops. Both of these methods will use up all of the yarn.
If you have any questions or comments on this guide, please email me and let me know.

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