In the last month’s blog, we discussed tromp-as-writ – treadle as written: given a twill, we can derive the treadling when using the standard tie-up for twills, that is, two treadles at a time, forming the diagonal that defines twills.

Below again is the pointed twill example: threaded 1, 2, 3, 4, 3, 2, repeat, the treadling sequence is also 1, 2, 3, 4, 3, 2, repeat. (Drawdown is rising shed.)

Tromp as writ can also be applied to block weaves, but it works best if we use a profile draft.

Below is a simple example of a profile draft. It tells us to thread block A, then B, C, D, C and B again (repeat). The tromp as writ treadling is to weave block A, block B, etc.

While profile drafts are extremely helpful when designing fabrics with block weaves, we must remember how many shafts we have available, because for each block, we must substitute the threading of that block.

Using the simple profile draft above, for summer and winter block A is threaded 1, 3, 2, 3; block B 1, 4, 2, 4, etc. Thus, we need six shafts to weave the 4-block profile draft.

For the tromp as writ treadling, we weave the treadling steps of block A, than block B, etc. The drawdown is below. It is sinking shed, even though I weave on rising shed looms; I find it easier to think of block weaves as having the weft cover the block: thus, for block A, shafts 1 and 3 followed by 2 and 3 are lowered, allowing the weft to cover the warp on those shafts. The tie shafts, 1 and 2, alternate in limiting the float; the resulting blocks are not solid and in the fabric background the warp peeks through.

The drawdown shown is a bit deceiving if we are not familiar with the structure. Every pattern pick of summer and winter is surrounded by tabby picks that form the background. Thus, we need two additional treadles to weave it.

Here is partial drawdown for block A that shows how our weaving actually proceeds:

Below is the fabric sample using the profile draft but woven with a different treadling; it does show the blocks and the background formed by the warp and ground tabby.

Profile drafts work best with tied unit weave of which summer and winter is one. The blocks are fixed; if we need a wider area, we simply increase the number of blocks, but the length of the floats stays the same.

Most tied unit weaves have a treadling generally associated with them, although many more options are possible. The drawdown above shows the treadling for summer and winter called single (each single pattern shaft is treadled with each tabby), while the fabric sample was woven using the treadling called “treadling o’s” because of the appearance of the blocks. Thus, the profile draft doesn’t specify which treadling to use, just the order of weaving of the blocks; the weaver chooses the treadling. (For more on summer and winter and its treadlings, see the entry in Block-Aid).

For other block structures, the weaver must make a decision as to the width of the block. For example, let’s use the same profile draft for overshot.

I learned block A of overshot as 1, 2, 1, 2. Others consider 1, 2 the kernel of the block. Either way, the block could also be 1, 2, 1, 2, 1, 2 and so on as long as shafts 1 and 2 alternate. The weft floats over the width of the block, so the size of the yarn should also determine the number of threads in that block. In a block too wide, the yarn will sag.

Block B of overshot is 2, 3, 2, 3. Shafts are shared between blocks, resulting in four blocks on four shafts. Thus, the profile draft we have been using could be applied to overshot on four shafts.

The blocks don’t have to be the same number of threads, just as long as each follows the definition: 2, 3 for B, 3, 4 for C, 4, 1 for D.

Below is the sinking shed drawdown we obtain when we use block threadings for the profile draft. As in summer & winter, each pattern pick is surrounded by a tabby pick. The tabbies are shown at the bottom of the drawdown. Overshot is derived from twills, so the tabbies are the classical 1 & 3 vs. 2 & 4. In contrast the tabbies for summer and winter are ties – 1 & 2 – vs. all pattern shafts.

Below is the fabric sample. Overshot has three classical areas: the overshot blocks made by the pattern weft, the plain weave blocks where the pattern weft floats on the other side of the fabric and the half-tones where the pattern weft peeks through the ground.

Below is another profile draft which illustrates both its usefulness and how well its use fits tied unit weaves.

We can substitute the blocks in the profile draft with a threading for a tied-unit weave shown in the drawdown below. This structure doesn’t have a common name, but can be classified as having two pattern shafts per block (3 & 4 for the first block), two ties that are unpaired because they are not next to each other (1 & 2 for all blocks) with a ratio of 1:2 (2 tie threads & 4 pattern threads or 2:4 is 1:2). This nomenclature of “double, two-unpaired ties, 1:2 ratio” is not unique, so we have to add what makes it unique: the pattern shafts are arranged in reverse pointed order with the ties.

The name is not important. What matters here is how wide the threading would be if we expanded the entire profile draft. Given the name and the threading of the first block, we can derive the rest of the threading.

There are two blocks A, three blocks B and two blocks C, three blocks B, then the repeat starts. Below is a fabric sample.

While the first profile draft in this blog was easily woven with overshot – or any other structure with variable width blocks – the profile draft we just used doesn’t easily convert: what does it mean to have two blocks of A in overshot, when one block can be as wide as we like? However, we could take this profile draft and adjust it for relative size: block A and C could be the same size, block B a third wider.

In designing, profile drafts are very useful. We can manipulate our tools to fit our needs.

Happy weaving!