Creating an Optical Illusion in Block Double Weave

 Perhaps it's because our brains just want to see patterns -- but do you see expanding circles in this drawdown?

But it's all squares, right? What's going on?

This is known as a "fiction illusion," in which the brain perceives a shape or figure that is not actually present in the image. Optical illusions involve different ways in which the brain and the eye process visual information, such that the perception is different from the reality. 

Why does this happen? Quoting from my Google search: "Your brain uses patterns, past experiences, and context to make sense of visual input, but illusions exploit these processes by presenting confusing or conflicting information, causing the brain to 'fill in the gaps' in a way that leads to a perception that doesn't match reality." 

Aha! Confusing or conflicting information, differences between perception and reality -- this is where weaving can createsome interesting patterns!

Our immediate perception of this black-and-white version of the pattern above: It's full of flowing lines that intersect, dilate, and compress.

But, in the weaving pattern, it's all black-and-white rectangles, increasing and decreasing in length and width. In weaver-speak, it's just double-weave blocks.

I'm in the process of dressing my loom with this design, which is simple block double weave on 8 shafts. Here's the threading:

Two blocks, that's it. But, if you look at the top of the threading, you'll see that the units of 1, 2, 3, and 4 descend from 9 to 8 to 7, etc., in number, all the way down to 3 -- and then they begin to expand again. This means that the widths of the two different warp blocks get progressively smaller, and then they reverse and get larger again.

The treadling is "tromp as writ," meaning that it's identical to the threading. ("Treadle as written" is my rough translation.)

Looking at the weft, you'll see the same progressive increases and decreases in the number of units per block -- from 9 units in the first block to 8 in the second to 7 in the third and so on down to 3, where the number of units begins to increase again. This means that the height of the blocks changes, getting progressively longer and then progressively shorter.

The beauty of double weave is you get solid colors: In the case of my drawdown at the top of this post, green weaves with green, in alternating blocks that are either on the top layer or the bottom layer. And red is doing the reverse. Double weave makes for bold colors and graphic patterns, which is probably why weavers like it so much.

Here's the tieup. It's a double-weave tieup, so that the first 4 shafts on the first treadle lift just shaft 3, while the second 4 shafts weave the bottom layer, which is being woven upside down. This means that, effectively, shaft 7, which is technically down, is the only shaft lifted on the upside-down bottom layer. Then, on treadle 2, the layers exchange, so that shaft 8 is lifting the warp on the top layer while shaft 2 is "lifted" on the upside-down bottom layer. You're exchanging the top layer and the bottom layer to form differing rectangles. And effectively you're weaving plain weave on both layers. (Caveat: I don't consider myself a double-weave expert, so I simply created a tieup that works for me.)

The structure itself gives you two layers of cloth that exchange (top to bottom) in the pattern we talked about, squares that 

increase and decrease in height and width. In my case, I'm threading everything in beige -- but one layer is 20/2 wool and 

the other layer is 17/2 nm silk noil. Using differential-shrinkage techniques (where the wool fulls and draws in 

and the silk noil buckles and puckers because it's being drawn in by the wool), I hope to end up with a fabric that has a 

really interesting texture. But I haven't finished threading yet ;o) because I had to re-thread to get the pattern just right....

And my loom's acting up, but that's another story. Fingers crossed. 

Thanks for reading!