Determining the correct sett for your project can be a bit of a challenge. If the same yarn is used in both warp and weft, the following formula should result in a balanced weave structure.
W = Wrap the yarn around a ruler, with the yarn just touching, to determine the number of wraps per inch.
I = Study the weave structure of the pattern you wish to use, and determine the number of intersections in the pattern repeat. Each time the weft travels from the front to the back of the fabric, passing between warp threads, this is counted as an intersection.
i.e. in a tabby weave there are 2 intersections in any given 2 warp threads.
in a twill weave there are 2 intersections in any 4 threads.
R = Determine the number of warp and weft threads in one repeat of the pattern.
Sett = W – ((I * W) / (I+R))
Yarn: 10/2 Cotton
W = 35
I = 2
R = 2
Sett = 35 – ((2 * 35) / (2 + 2))
Sett = 18
I = 2
R = 4
Sett = 35 – ((2 * 35)/ (2 + 4))
Sett = 23.4
The result can be rounded up to a sett of 24 epi. It is best to weave a small sample, and wash or wet finish it. As each weaver has a different ‘hand’ or weaves with a slightly different tension, the resulting fabric may yield a product. The sett will have to be adjusted to obtain the desired result. Also, depending on the drape or use of the fabric, the sett may be changed from 10% – 30 %. For a looser weave structure such as lacey curtains, the sett would be reduced. For tight weaves, such as upholstery, increase the sett.