If you start a weaving project with a pattern, there will be a yarn suggested, but what if you have some other yarn you think would work? Or what if you don’t have a pattern, but have lovely yarn to weave?
This is where we get back to the “wraps per inch” (w.p.i.) and a ruler, which were mentioned in my last post.
You need to take your yarn and wrap it around a ruler, covering an inch without wrapping the yarn too tightly (you don’t want to stretch it and make it thinner) and with each wrap just touching.
Then you count how many strands are filling that inch of ruler and this is your w.p.i. But, if we tried to weave that, there’d be no room for the weft to pop under/over our warp, which is why you need to halve the w.p.i. to get your e.p.i. (ends per inch / weft threads per inch) for plain weave – twill is different. By the way, e.p.i. is also refered to as the “sett”.
Getting this right should give you a nice balanced weave for that yarn.
For example, if you have a yarn that gives a count of 14 w.p.i. you know you should be aiming to weave at 7 e.p.i. That means you want to use a reed where the dents are spaced at as close to 7 dents per inch (d.p.i.) as possible.
Where you are looking to substituted a yarn for what’s suggested in a pattern; are you getting the same e.p.i. with your yarn? Standard sized reeds are generally going to match up to a standard sized in yarn, but you should test to be sure.
If, like me, you pick yarns and freeform a scarf, then you usually want to use the right reed for the yarn. Though, if you want to make a denser cloth (higher e.p.i.) / more open cloth (lower e.p.i.), you’ll know which reed to try, based on the “ideal” d.p.i. for that yarn.