I have been working on a project for a book where the yarn quantities will be quoted in yards and metres and not balls. This is to enable the knitter to use any yarn they wish provided that the tension is the same. In the spirit of the project, I bought four balls of branded DK complete with ball bands from a charity shop and a cone of unbranded (without ball band) yarn from another charity shop. "That's OK," I thought. I can work out the number of stitches in the project, then work a sample or two to find out the length needed for so many stitches and work back. Then add on extras for the ends when casting on and changing colours, sewing up, etc.
Both yarns fortunately knitted to the same tension. The branded balls were OK for calculating the length used as the weight and yardage were on the ball band.
Um. Measuring the coned yarn was not as easy as I thought. Even knowing the weight used was no good without the weight-per-length. We have an old wooden yardstick so I duly measured a length of coned yarn, the same length of the branded yarn, and the same lengths of other yarns with the same ball band tensions. The same lengths of all these yarns knitted up to different numbers of stitches. The yarns had all been measured 'relaxed', without allowing for the stretch and tension control when knitting.
Next step was to knit a known number of stitches with each yarn and then measure the yarn used. When the yarn was measured 'relaxed' and when measured 'taut' (that is, to the full extent of its elasticity) the lengths for the number of stitches per yard changed considerbaly for some and not so for others. However, the number of stitches per yard for the 'taut' measurement were similar for each yarn used.
I spent many hours on the internet trying to find how to measure yarns (relaxed, taut, whatever) when the yardage is not given on a ball band but without success. I asked on Ravelry but without the answer (yet). Answers did include what I would have done anyway, revert to the weighing the product of a known number of stitches and calculating the length from the ball band info. (But my point is that the ball band info wasn't there!)
Anyway, I have come to the conclusion, rightly or wrongly, that the yarns should be measured taut. If measured relaxed the different elasticity of the different yarns is not taken into account. In the meantime I am knitting up samples of different yarns with the same ball band tension and the known weight per yard calculated from the ball band, and checking that the number of stitches per yard are the same. I'll keep you updated.
One wonders how other knitters measure their yarn.
If you have any knowledge, comments, etc to pass on about this then do please tell.