Designing Shadow Weave – the Atwater System

According to modern sources[1], the shadow weave was developed by Mary Meigs Atwater and first published in The Shuttle Craft Guild Handweaver’s Bulletin in 1942. Because most of the Shuttle Craft publications which described shadow weave are long out of print, most of us will need to rely on secondary sources for design directions (see Bibliography at the end of this handout).

1. The Tie-Up

There is also another method of producing shadow weave, worked out by Marian Powell. When examining shadow weave drafts in publications, it is easy to identify which system has been used by looking at the tie-up. The Atwater system uses a simple twill tie-up for

shadow weave:

4 / 4
3 / 3
2 / 2
1 / 1
6 / 6 / 6
5 / 5 / 5
4 / 4 / 4
3 / 3 / 3
2 / 2 / 2
1 / 1 / 1
8 / 8 / 8 / 8
7 / 7 / 7 / 7
6 / 6 / 6 / 6
5 / 5 / 5 / 5
4 / 4 / 4 / 4
3 / 3 / 3 / 3
2 / 2 / 2 / 2
1 / 1 / 1 / 1

Four harness

Six harness

Eight harness

2. Determining shadow “pairs”

Each unit of a shadow weave pattern is formed by a pair of threads of contrasting characteristics (dark/light; thick/thin; bumpy/smooth; dull/shiny, etc). In most draft descriptions the “dark/light” terminology is used. A block unit, then, is a pair of threads, one dark and the other light. It’s odd – although we think of a “shadow” as being something dark, in shadow weave we consider the dark partner to be the primary one, and the light partner to be the “shadow” one.

There are several ways that selecting the Atwater pair partners has been described:

Mimi Smith[2] uses arithmetic: the shadow thread for harness 1 is determined by “(number of shafts divided by 2) + 1”. For a four-shaft loom, that would be (4/2)+1 = (2)+1 = shaft 3. So the first pair would be shaft 1 dark, shaft 3 light. For six shafts, (6/2)+1 = 4; the first pair would be shaft 1 dark, shaft 4 light. For eight shafts, it works out to shaft 1 and shaft 5. The remaining pairs follow in progression: after 1D/3L comes 2D/4L, 3D/1L, 4D/2L, etc.

For the more visually minded, Lucille Landis[3] uses a pictorial approach:

She draws a circle diagram and draws lines between the partners:

Another way to think about it is just to write the harnesses in two lines:

1 2 1 2 3 1 2 3 4

3 4 4 5 6 5 6 7 8

3. Determining Threading Units

Now that we have identified our pairs, we can work out our block units. Each pair can create two different pattern units – one if the threading is dark-light, and the other if the threading is light-dark. For example:

Four harnesses have two pairs of partners, but four pattern blocks:

1D-3L and 1L-3D; 2D-4L and 2L-4D

or, you can think of them in numerical order by the primary (dark) partner:

1D-3L, 2D-4L, 3D-1L, 4D-2L

Exercise: What are the threading units for six and eight harnesses?

4. Select a Profile Draft

Now we know how many blocks or units we have to work with. Next we can design a profile draft of the blocks we want to use.

Just about any threading pattern can be converted to shadow weave. A good place to start is with a twill threading. Point twills and undulating twills make especially successful shadow weaves, and offer opportunities for a number of treadling variations. Later on, you might want to convert an overshot pattern to shadow weave.

Let’s look at this threading for a simple twill pattern as if it were a profile draft. Each square, instead of representing one warp thread, represents one shadow weave unit – a pair of threads in a dark/light or light/dark sequence. We can also name the block for its primary thread (Block 1, 2, 3, or 4).

Block 4 – 4D/2L

Block 3 – 3D/1L

Block 2 – 2D/4L

Block 1 – 1D/3L

One way to convert this to a shadow weave threading is to redraw it with spaces between the filled-in blocks, and then fill in the “shadow” partner:

With this threading and tieup, and treadling “as drawn in”, the twill lines are followed by the shadow pattern with a “featherstitching” effect on its edges. This is called “twill fashion” or “twill development.”

If you convert one threading unit to multiple shadow weave unit repeats, you get a different effect, and it is called “block development.”

Here we see the “shadow” effect more clearly. It appears as if the weave is three-dimensional, and the light source is coming from the upper left corner. We do not see the “featherstitching” outlining the blocks.

Treadling

If you examine the treadling sequence that results when a draft is treadled “as drawn in”, you will see that we are treadling on opposites. If we look at the threading pairs – 1 & 3 and 2 & 4 for four harnesses; 1 & 5, 2&6, 3&7, 4& 8 for eight harnesses – you will note that, using the twill tieup, the corresponding treadle numbers are tied to opposite pairs of harnesses.

1 2 3 4 1 2 3 4 5 6 7 8

Other types of treadling are possible, but they will give different effects.

Working with Points and Reversals

The only remaining design issue to keep in mind is the handling of patterns which ascend or descend to a point, and then reverse. There are two “rules” to follow for standard shadow weave results:

1. When you are “ascending” a twill line (going from low harness numbers to high harness numbers), the dark partner goes first. When you are descending, the light partner goes first. The descending line is a mirror image of the ascending line.

2. In order to keep the alternating dark/light color order constant, you need to either add or remove one thread at the reversal points.

Example: Using a simple profile sequence of 1-2-3-4-3-2-1:

Ascending: 1D/3L – 2D/4L – 3D/1L

Point: 4D OR 4D/2L/4D

Descending: 1L/3D – 4L/2D – 3L/1D

Here is what it looks like if you follow these rules for a twill-fashion development:

Note that a thread is dropped at the bottom point (1) as well as the top point (4). There are two repeats here : (123432 1 234321)

But this is what you get if you don’t:

This threading does not change with the turning point and descending line: it is threaded

1D/3L – 2D/4L – 3D/1L – 4D/2L -3D/1L – 2D/4L – 1D/3L

The descending line doesn’t carry the light partners first, and the point does not add or drop a thread.

For block development, however, it is not so clear whether one should follow these rules. Below is the same point twill design, threaded block fashion (four units per block), with

the specified adjustments.

Compare this with the drawdown on the next page.

This drawdown has the following characteristics:

1. The blocks at the points are complete; no thread is dropped.

2. The descending sequence remains dark before light.

3. However, the descending partners are still reversed, so they mirror the ascending threading numbers (not colors.).

Notice that the shadow effect is much more pronounced here; the light source again appears to be on the upper left, and the fabric appears to be three-dimensional.

Summary

The following guidelines, then, may be used to summarize the steps for designing with Atwater shadow weave:

1. Always begin with a twill tie-up.

2. Based on the number of harnesses you wish to use (always an even number), determine your threading units (harness pairs and color sequences).

3. Sketch a profile draft.

4. Determine if you want to make adjustments at turning points and reversals.

5. Substitute the appropriate shadow weave unit for each block in your profile.

6. For standard results, treadle as-drawn-in.

7. Variability may be introduced by trying different color sequences in warp and weft, by experimenting with different adjustments at turning points, by modifying color combinations, and by using different treadlings.

Bibliography:

Shuttle Craft Guild Handweaver’s Bulletin, 1942 (Atwater) and June/July 1953 (Tidball).

Handwoven, March/April 1998, “Exploring Shadow Weave”, “In and Out of the Shadows,” “Turned Shadow Twills.”

Atwater, Mary Meigs – Mary Meigs Atwater Recipe Book, Salt Lake City:Wheelwright, 1986.

Lucille Landis, Twills and Twill Derivatives, Old Greenwhich, CT: self-published, 1977

Mimi Smith, “Atwater-Powell Shadow Weave”, Shuttle, Spindle, and Dyepot, Winter 2003-4

Strickler, Carol, Editor, A Weaver’s Book of 8-Shaft Patterns, Loveland, CO:Interweave Press, 1991.

[1] Mimi Smith, “Atwater-Powell Shadow Weave”, Shuttle, Spindle, and Dyepot, Winter 2003-4, p. 54

[2] Ibid., p. 54

[3] Lucille Landis, Twills and Twill Derivatives, Old Greenwhich, CT: 1977, p. 113.