Monday, February 18, 2013

Bent-wire crochet

Wire crochet is usually formed on a hook, the wire being bent as each stitch is made. Using this traditional technique, it is difficult to precisely or variably size the gauge of the stitches. Also, when heavy steel wire is being worked (as for concrete reinforcement,) the size of the hook and the strength to wield it can be limiting.

Alternatively, in a new technique, crochet stitches can be assembled from machine-formed wire coils. The pre-formed coils precisely set the size of each stitch, and most of the strenuous bending will have already been accomplished by a computer-controlled machine.

A right-hander's chain stitch viewed from the front.

The same chain viewed from the rear.

Crochet, though it often looks complicated, consists solely of the chain stitch and the various ways the chain stitch can be worked through itself. The more modern crochet stitches, i.e., those introduced in the nineteenth century—the treble crochet for example—are actually nothing but a short length of chain stitch worked in a different way. Thus, there is essentially only one kind of stitch that needs to be machine-formed in the coil.

There are two ways to form a chain stitch, one more familiar to sailors (The Ashley Book of Knots #2868), the other more familiar to crocheters. Both are relevant here. The sailor's technique is to form hitches and push them through the chain, the crocheter's technique is to form loops on a hook and pull them through the chain.

Ashley shows the hitches being formed in front of the chain and being pushed down through it. From a crocheter's perspective, this is working from the backside, so Ashley's drawing is a rear view of a chain. But a sailor might just as well form the hitches behind the chain, and push them up through the chain, giving a perfect correspondence with a crocheter's perspective.

 If all the hitches to be made in the sailor's technique are made in advance, the result is a coil of wire that gets pushed through the growing chain one turn at a time.

In crochet, by convention, the front side of the chain stitch is the side that the hook enters from. The appearance of the stitch as viewed from the front will depend on whether the crocheter is left- or right-handed, but it can be fancifully described in both cases (see image of a right-hander's chain stitch above) as looking like a trail left by horseshoes, the crotcheter having progressed in the same direction as the horse.

One link of a chain stitch.

Since the chain stitch is periodic, any way of cutting a chain into lengths one-period long will reveal it to be composed of identical pieces. I find it convenient to imagine segmenting the chain into links that look like horseshoes having a long leg and a short leg. The long leg (the first-formed part of the stitch) is a simple straight run, the short leg (the last-formed part of the stitch) ends in a bend transverse to the plane of the horseshoe. These transverse bends protrude on the back side of the chain like vertebrae on a swimmer's back. That makes it easy to remember how to tell the front of a chain stitch from the back.

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