Substituting Doubled Yarns
I am gearing up to attempt Mary Berent’s 4-shaft overshot project from pages 38–40 in theNovember/December 2010 issue of Handwoven. I am relatively new to using a 4-shaft loom (I'm a previous rigid-heddle weaver). The pattern calls for 2 ends of 20/2 pearl cotton to be warped together with the warp sett at 30 epi. According to the the Master Yarn Chart, 20/2 sett at 30 epi is for a lace weight fabric. Since the 20/2 is doubled, would that be equivalent to 10/2 as a single end (20/2 @ 8,400 yd/lb, and 10/2 @ 4,200 yd/lb)? I have 8/2 cotton that I’d like to use instead. Should I use sett of 24 epi?
In the project you are citing, the two ends of 20/2 are wound together, but threaded separately. So there are 30 single 20/2 ends per inch. Because of the overshot pattern weft, which is woven in every other pick, the warp sett of 30 ends per inch will produce a fairly firm fabric (there will be 60 picks per inch, 30 tabby, 30 pattern). 20/2 could also be sett at 36 epi, but an even firmer beat would be required to square the design (the usual intention in overshot is for the plain weave ground cloth to be balanced, so this would mean 36 tabby picks per inch for a total of 72 ppi with the pattern weft).
For 8/2 cotton, you should sett the warp at 20 ends per inch. To produce a runner using Mary Berent's draft, you will have to reduce the number of repeats unless you want the 19-1/2 inch runner in 20/2 to be 28-3/4 inches wide in 8/2 (575 ends divided by 20). There are 32 ends in each of those little flowers in the center. So if you do 3x instead of 6x for that 6x repeat (3rd row of the draft) you'd be eliminating 96 ends or 4-4/5 inches, but your runner would still be over 24 inches wide. 3/2 pearl cotton would be the right size for pattern weft.
Welcome to shaft-loom weaving!