I'm back to weaving - or trying to, in between book shipping distractions - and decided the easiest thing to do would be to weave up all those scarf warps I wound before Christmas.
As I was weaving today I thought about the yarns we choose to work with and how to determine an appropriate density for the cloth we intend to create.
Some yarns/qualities of cloth just need more elbow room than the standard charts recommend.
For instance with these warps I'm using two different yarns. The green is a lightly textured rayon which may well be cabled (I haven't deconstructed it to find out how exactly it was spun) and a textured rayon 'boucle' (the purple).
The boucle (I call it that because I'm not sure what exactly to call it - again I've not deconstructed it to find out how it was spun) is thinner than the other, over all. But the texture of it means that it needs more elbow room. I think you can see in the photo that parts of the yarn are quite a bit thicker than the other. The density of the cloth needs to take that intermittent thickness into consideration or else the resulting cloth will be tighter and stiffer than I really want for a scarf.
Another yarn that needs to have density adjusted is linen. While a linen yarn may be the same thickness as a cotton yarn, the fact that the linen is denser than cotton, and stiffer than cotton, means it needs to have more elbow room than cotton.
Charts giving standard recommendations for various yarns are always just a starting point.
One of the challenges in the master weaving program through Olds is to weave sett samples. In level one the yarn is wool; in level two the yarn is cotton.
Students always want to know what the 'right' density is. The truth is that there is no right density. For 2/8 cotton I've seen charts telling people to use 2/8 cotton for plain weave anywhere from 18 to 24 epi. And you can. Using the different degrees of density can be done but cloth of completely different qualities will result. 18 epi/ppi will make a much better towel than one at 24 because the denser and stiffer the cloth, the less absorbent it will be. The higher density will, however, be much more durable in terms of abrasion resistance.
Whether someone does a yarn/ruler wrap, uses the Ashenhurst formula, or follows the recommendations of a chart, remember that those numbers are just a starting place. The yarn being used may require more - or less - elbow room, depending on the quality of the cloth desired.
This is why we weave samples.