Double twill is a structure I wove a lot of nine or ten years ago. It involved two warps, light & dark, and (at that time) 4 wefts, usually red, blue, yellow & green. There are many color possibilities with that arrangement; The twill in the top layer can have either a light or a dark warp, and any one, two, or three of the colored wefts; in addition, the twill on top can be 1/3, 2/2, or 3/1. Multiplying all that out, you get 84 color possibilities. For more information about this interesting structure, refer to Chapter 8 of The Woven Pixel (see sidebar).
I'm returning to the double twill structure for an upcoming project, but I've decided to work with the 3-weft version instead. There will be black & white warps, and the three wefts can be used one or two at a time, with the three different twills and either a dark or a light warp on top. This multiplies out to 36 color possibilities, still a gracious plenty.
My loom is currently set up to weave at 60 epi, and it has a black warp on it, so I can't do a true color sample until I rewarp it with black and white. But I can still get a lot of information from a sample. What I specifically want to know is what weft weight will work best with the 20/2 cotton warp set at 60 epi. I wove a small sample this morning, first with 20/2 cotton as the weft, and next with 10/2 cotton.
I learned a lot. The 20/2 cotton weaves to 96 ppi in this structure, while the 10/2 cotton weaves to 72 ppi. I'm liking the 10/2 version much better, and after I rewarp the loom in black & white, I'll do a real weave blanket to see all 36 colors.
Meanwhile, here's a digital simulation of the weave blanket. It looks better if you click on it to enlarge.
I've added a new category, Double Twill, to my list. I'll be using Weaverly to document the progress of this project (my virtual notebook, if you like), so if you want to follow along, Double Twill is the ticket.