Tuesday, October 18, 2011

Why (some of us) Use Computer-Driven Looms

In my last two posts I hope I’ve convinced you that computer-driven looms are not miraculous labor-saving devices that produce woven textiles while you sit back and enjoy a margarita. So, why do we use them?

The reason is because of the design flexibility they give us. There are really two parts to this.

First, it allows us to have looms with more shafts. The more shafts we have the more intricate the designs we can weave. Looms have treadles (pedals) that look like the pedals on an organ. They control the lifting of the shafts and that produces the design. On manual looms it is typical to have two more treadles than shafts. A four-shaft loom would have six treadles, and eight-shaft loom would have ten, etc. Because there is a limit to how many treadles you can reach without falling off the bench, a practical limit to manual looms is about 16 shafts and 18 treadles. To get a loom with more than 16 shafts it almost has to be computer-driven.

The second part is the really interesting feature of computer-driven looms and the main reason we get more design flexibility. This involves math but it’s not hard math and if you’re not a mathematician (I am) you can just believe my numbers. As a simple example, on a four-shaft loom there are 14 different combinations in which you can lift those four shafts:

  • There are 4 ways to lift one shaft: 1, 2, 3, or 4
  • There are 6 ways to lift two shafts: 12, 13, 14, 23, 24 or 34
  • And, there are 4 ways to lift three shafts: 123, 124, 134, or 234

I said earlier that a four-shaft loom would normally have six treadles. Each treadle can be tied-up to any one of those 14 combinations. So, we can use six of the 14 combinations but not the other eight. With a computer-driven loom we can use all 14 since there are no treadles and the computer controls which shafts get lifted each time.

Now, with an eight-shaft loom, (here comes the math) there are 254 combinations and with a manual loom we can only use ten of them. On a 16 shaft loom there are 65,534 combinations and a manual loom can only use 18 of them. With a computer driven loom you can use any of the 65,534 at any time. (Practically speaking, a typical scarf, e.g., might only have 2,000 or so weft threads, so you couldn’t actually use all 65,534 but the point is that you could use any of them at any time, not just one of the 18 that would be available on a manual loom.)

You can see that the more shafts we have, the more limiting the manual loom becomes. The numbers go up dramatically and with 24, 32, or even 40-shaft looms the combinations are astronomical.

So, that’s why we do it. It takes a while to learn how to design with all this added flexibility but once you’ve figured it out it opens up some amazing design possibilities.

Yesterday was jury day and we now have a brand new show in the gallery. This month’s theme is Fissures, Fossils and Fragments and, as usual, the gallery is again full of  wonderful pieces. In my next few posts, I’ll have photos and artists statements from the artists who received special recognition from the jurors.

(Posted by Larry Novak)

1 comment:

BlueLoom said...

Great post, Larry! Even a mathophobe like me enjoyed it.