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From Four to More

Marcy Petrini

5/2/2016

 

In last week’s blog I mentioned that I like to think of two methods for extending weaving structures from four to eight shafts; one way is to simply extend the threading; the other way is to divide the eight shafts into two sets, which I call the “front” loom (1, 2, 3, 4) and the “back” loom (5, 6, 7, 8).

The methods are not clear cut, but they have helped my students use those extra shafts. Surveys have shown that weavers buy eight shaft looms, but often just use four, perhaps because there can be some difficulties – namely floats – that have to be solved with the extension.

We can apply the two methods to overshot and monks’ belts. For a simple extension to eight shafts, the four-blocks of overshot listed last week become:

Block A

1, 2, 1, 2, repeat

Block B

2, 3, 2, 3, repeat

Block C

3, 4, 3, 4, repeat

Block D

4, 5, 4, 5, repeat

Block E

5, 6, 5, 6, repeat

Block F

6, 7, 6, 7, repeat

Block G

7, 8, 7, 8, repeat

Block H

8, 1, 8, 1, repeat

 

The process works for threading, but the treadling presents the float difficulty. Look at the drawdown below where the blocks were woven one at a time, as it is done in 4-shaft overshot. This is for a sinking shed loom. As in four shafts, when we weave one block, shown in yellow weft here, we obtain half tones in the two adjacent blocks; the problem becomes that there are five blocks remaining; the solid red represents areas of plain weave, since the drawdown only shows the pattern weft; but wherever plain weave appears on this side of the cloth, there will be weft floats on the other. Treadling a single block produces continuous floats over five blocks (right click to open a larger image in a new tab).

The solution is to break up the blocks in the threading, or combine blocks in the treadling, or vary the size of the blocks, or a combination of these.

For monks’ belts, we can use the idea of a front and back loom; these are the blocks:

 

“Front” Loom

“Back” Loom

Block A

1, 2, 1, 2, repeat

Block C

5, 6, 5, 6, repeat

Block B

3, 4, 3, 4, repeat

Block D

7, 8, 7, 8, repeat

 

Then in treadling, we have to weave the front and back looms at the same time. We already know from four shafts that only one block at a time can be woven because of the floats, with two looms, we can have four possible combinations: block A with either C or D; and block B with either C or D.

However, the float problem persists, but not as extensive as in overshot: there are two combinations that are viable. Look at the drawdown below, also for a sinking shed loom. The orange represents areas of weft floats; whenever the floats are over two blocks, they are too long. The blue represents areas of plain weave, which, however, are floats on the other side of the fabric. Thus, for this threading, A & C, and B & D produce reasonable floats.

In this case, using the front and back loom idea helped us eliminate some floats. If we had extended the threading for monks’ belts as we did in overshot, we would have started weaving one block at a time, and it would have taken us longer to arrive at the combinations that work.

This front-and-back-loom method works particularly well when we want to combine structures. We could weave a twill in the front loom and huck in the back loom. Even without extending the threading, the possibilities are staggering.

 

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