Sett

or How to Work Out Which Yarn to Use with Your Rigid Heddle Loom

I've been asked how to work out whether a yarn is suitable for weaving on a rigid heddle loom and have been trying to explain about wraps to the inch.  I decided it was much better to do this via this blog!

On the right is an image of a yarn wrapped round a stick (this could be a pencil or pen or even straight round the ruler!).  You should see that it's been loosely wound so that the yarn isn't stretched, which would make the yarn narrower and give a false number of wraps.  There are 14 wraps to the inch with this yarn.

If you take a cross section of a balanced plain weave you will see  there are equal numbers of warp thread to weft threads.  So with our 14 wraps every wrap would alternate as either a warp or weft thread, so we can safely say that half the wraps would be warps and half would be wefts.
That would make 7 warps and 7 wefts = 14 wraps.
Therefore with 7 warps (S) we could use a 7.5 epi reed, the nearest in number to our yarn.

If a very open and softly draping shawl was being made we could go for a 5 dent reed or if we wanted firm upholstery fabric we might use a 10 dent reed.   We work this out by taking the wraps number, in this case 14, and divide it by 2 to get the sett for a balanced plain weave, 7 (S) here.  To allow for extra drape we can decrease that number by 5 - 10%, here that would be 0.7 at 10% which is approx. 1 end.  Take this from 7 (S) to give 6 ends, and you will see that the nearest reed is the 5 dent reed.

If you are using a slippery yarn to make a scarf, decrease S by 5% for drape but increase by 20% for slipperiness, a net increase of 15%.
For upholstery fabric increase S by 15 - 20% and beat very hard to obtain a balanced cloth.

I hope this helps!