Advancing Twills

Marcy Petrini

2/1/2016

A shawl woven in a 40-shaft advancing twill just came off my AVL loom. Here is a preliminary photo – a much better photo must wait until Terry can take it.

You can see the bands of warp (red-purple) and weft (blue-purple) interlacing. I love advancing twills and what I like about my 40-shaft loom are two major advantages: one is that a complicated treadling has to be entered once and then becomes automatic; yes, I must pay attention to avoid accidentally skipping a step which can be easily done and cumbersome to undo. But this particular twill is threaded as a straight draw 1 to 40 and has a treadling repeat of 239 steps. Clearly I wouldn’t be able to weave that easily without a computerized dobby.

The other advantage is that it forces me to design the structures from scratch, there is no reference – “green book” or “red book” – for 40-shaft structures. I must understand the structure pretty well to come up with the cloth I want.

Advancing twills can be woven with many fewer shafts; on 4-shafts, the “advancing” generally occurs in the threading and, for a more complicated motif, the treadling. Here is the draft of an example (for a better view, try to left-click, or maybe right-click, the draft and open in a new window that will appear under the current tab):

From the threading and treadling we can see why it’s called an advancing twill: one shaft is deleted at the beginning and one shaft added at the end of a straight twill repeat to make the next repeat. Here there is a complete repeat of a straight twill to start the threading of the motif, but that’s not necessary. And other twills, like pointed, can serve as the starting point of the advancing twill.

Here is the fabric that corresponds to the draft:

The treadling sequence for this advancing twill is 16 shots long, not too bad. We can simplify it by using a straight twill treadling, and that results in an interesting zig-zag motif down the fabric as shown in the draft below:

For an interesting twill “line”, try to advance a twill!

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