What Sett Actually Means

Sett is simply how many warp threads you place in a given width of cloth. In the UK you will see it written as ends per inch (epi), and in older pattern books as "sett" or sometimes "reed count". The two ideas are cousins, but not twins: the reed count is how many slots (dents) your reed has per inch, while sett is how many ends you actually thread. If you have a 10-dent reed and thread two ends in every dent, your sett is 20 epi. Sley one end per dent and it drops to 10 epi, without changing the reed.

Get sett right and everything downstream becomes easier. The cloth has a pleasing hand, the warp doesn't fray or snap with every shuttle pass, and the weft beats in comfortably rather than fighting for space. Get it wrong and you will know within a few inches: too close and the shed sticks, the warp abrades, and the cloth comes out like cardboard; too wide and the weft slides about, you get gaps you could post a letter through, and the finished piece feels flimsy.

Why Sett Is a Starting Point, Not a Rule

Sett is a relationship between three things: yarn thickness, weave structure, and how you want the finished cloth to behave. A fine 2/28 Nm lambswool and a chunky handspun aran will not share a sett, and neither should a plain weave and a 2/2 twill in the same yarn.

The reason comes down to interlacement. Plain weave has the most intersections per inch, so the threads are forced apart and need more room. Twills, satins and lace weaves let yarns sit closer together because they float over their neighbours. A denser structure also means more abrasion, which is why slippery or weak yarns benefit from a slightly open sett.

Finding Your Sett with the Wrap Method

The quickest practical check is the wrap method, and it needs nothing more than a ruler and a little patience.

• Wrap your yarn around a ruler for exactly one inch (or 25 mm), keeping the threads snug against each other but not squashed or doubled over.
• Count the wraps. That number is your wraps per inch, or wpi.
• Repeat three times, in different places on the ball or cone, and take the average. Handspun and slubby yarns can vary by several wraps.

Now apply a rough rule for the structure you intend to weave:

• Balanced plain weave: sett is around half your wpi. Twenty wraps per inch gives a sett of 10 epi.
• Twill: roughly two-thirds of wpi, so 20 wpi suggests about 13 to 14 epi.
• Weft-faced or rug work: a third of wpi or less, so the weft can pack in and cover the warp.
• Lace, huck and open fabrics: start wider than the plain weave figure and sample before committing.

Adjust for character. Fluffy woollens that full in the wash want a slightly wider sett than the maths suggests, sometimes 10 to 20 per cent wider. Slippery high-twist silks, linens and cottons want to be a touch closer so the cloth doesn't shift.

Working Backwards from Your Reed

Once you have a sett figure, check it against the reeds you own. If your target is 12 epi and you have a 6-dent reed, thread two ends per dent and you are away. For awkward numbers, skip dents in a repeating pattern — for 15 epi in a 10-dent reed, sley 2, 1, 2, 1, 2, 1 and so on. Metric reeds sold as dents per 10 cm convert easily: 40 dents per 10 cm is about 10 dents per inch.

Also remember that sett and picks per inch are separate numbers. For balanced plain weave in the same yarn, your weft beat should end up close to your sett, but the cloth on the loom will not look balanced. It will look sleazy and slightly gappy. That is normal. Threads swell and shift during wet-finishing, and the fabric you pull off the loom is not the fabric you will use.

Fine-Tuning, Sampling and Records

Treat every calculated sett as a hypothesis. Warp a sample at least 15 cm wide with a few inches of weaving, cut it off, wash it the way you intend to wash the finished item, and let it dry flat. Then judge it with your hands: does it drape, does it hold a shape, can you see daylight when held to a window?

Keep a notebook or a card for each warp. Record the yarn and count, the structure, the reed and sleying order, the sett, the picks per inch, and what happened after finishing. After a dozen entries you will have your own reference table, far more useful than any chart, because it will be tuned to the yarns you actually buy and the water you actually have.