Weaving from a “brick grid” talim

Looking, or imagining you’re looking, at a design drafted on a brick grid instead of the more common square grid, raises the question, what do you do with the half “bricks” found at the ends of every second row? It’s a more important issue than just the half-bricks themselves, because they determine the position of the rest of the bricks in the row and their design information, in relation to the rows above and below.

But this “problem”, or quirk of visualization, would not have arisen historically in the talim system of designing for Kashmiri twill-tapestry shawls, if it didn’t correspond to a feature of the traditional weave structure, 2/2 twill. In this structure, each weave unit consists of four warp threads and four weft threads. Four weft threads tells you that each cycle of the weaving requires four treadlings. In each treadling two adjacent warp threads are raised, becoming a visible pair or “nal”, and the other two lowered and basically disregarded. In the next treadling, the two warp threads that are raised shifts by one thread to the right, and so on through the cycle of four treadlings, so in the fifth treadling the same two warp threads are raised, as in the first treadling. It will be observed that in one, and only one, of the four treadlings, a single warp thread is raised at the left-hand edge of the cloth. Voilà, the “half” brick.
In the old talim system, each line of instructions is followed for two picks of weaving, two complete rows of weft threads, two treadlings. The count of nals in each line is the same, so for the lines which include half-nals, the count is completed by adding 1/2 at the beginning and end to the number of whole nals between. My practice is to make the treadling where the single warp thread appears on the left, the first pick worked according to the talim line of instructions that begins with a half-nal. In this pick, all wefts are moving from left to right, and at the right-hand side the other single warp thread will be found, completing the count as expected. At the next treadling, because the pairs of raised warp threads are advancing to the right, the single raised warp thread at the right-hand side disappears. Begin inserting the weft threads from right to left, subtracting the missing half-nal. When you reach the left-hand side you will find the missing warp thread has reappeared to form a pair with the single warp on the left, providing a count one whole nal more than expected – that is, instead of 3 1/2 when you started that line of instructions, for example, it now looks like four. This is correct.
Talim lines beginning with whole nals proceed exactly as written, in both directions. It is only in the second treadling of the half-nal talim lines, that there is potential for confusion about a mistake in counting.

The Generate Text Summary function of my Stitch Painter program is not sophisticated enough to put in half-unit counts at the ends of the appropriate lines, so I select the grid area to make sure that the odd-numbered lines of the text summary will have counts totaling one nal less than the even-numbered lines, and I remember to add the half-nals mentally to the odd-numbered lines when weaving.