The terms warp and weft are primarily associated with weaving but are also used when describing looped fabric, for example, as designations for the two basic forms of industrial machine knitting. A “weft knitting machine” drapes a continuous “weft thread” across a battery of parallel hooks that work it into a “course” (row) of loops from the one side of the fabric to the other. A second course is then knitted into it, releasing completed stitches into the fabric, and the process is repeated until the desired length of fabric is attained.
The action of a weft knitting machine is seen in a snippet from a tutorial video (from a suite provided by the equipment manufacturer Groz-Beckert). The fabric being produced is termed Jersey in the industrial glossary, and plain knitting, stocking stitch, or stockinette in that of hand knitting.
One of the characteristics of this structure is the alignment of the stitches into “wales” (columns) parallel to the sides of the fabric. A “warp knitting machine” feeds one or more separate “warp threads” to each hook. There are several types of such machines. The basic action of the one called a “crochet machine” is demonstrated in another video from the same suite, forming a chain that is sometimes termed a “pillar stitch.”
The “warp guide” that wraps the thread around the hook when making this chain also transfers it to an adjacent wale, working the warp threads into a vertically aligned correlate to a weft-knitted structure. There is an obvious functional equivalence between the movement of the warp guide and needle in the machine, and the tandem action of the hook and fingers in hand crochet. Although less apparent, the chain along the warp is directly analogous to the vertical chain that is a fundamental component of the “post” in a tall crochet stitch.
Another type of warp knitting machine, a “tricot machine,” has two warp guides for every vertical structure, each with its own thread. I don’t know if the second guide could be adapted to produce the other component of a post, which is a spiral wrapped around it to which the chain is tethered. However, there is no similar mechanism for making the transverse chains that are another definitive attribute of hand crochet. A machine that can produce true crocheted fabric therefore remains to be devised.
The literature of industrial knitting accepts nonetheless that hand crochet bears the same relationship to warp knitting that hand knitting does to weft knitting (discussed here with additional illustrations and references to source documents). Hand knitters are unlikely to question this, particularly since there are weft knitting machines designed for home use. For the inverse reason, crocheters are more likely to regard the structural comparison as alien. Notwithstanding, the fundamental attribute of warp knitting is the production of fabric by making loops along a wale and working them them laterally into other wales.
These are also salient elements of crochet. Even its simplest forms involve the interlooping of adjacent wales and, as noted, taller stitches are additionally worked directly along the wale. The distinguishing characteristic of a crocheted post is the sequential working of proper loops held on the hook, into a spiral of one more wraps of yarn around it. Posts of varying height are illustrated in stitch atlases nearly from the outset of such publication. (A “long stitch” — quadruple or double treble UK — described by Mlle. Riego in 1848 is discussed here. The same stitch first appears in openwork Tunisian crochet in a publication by Cornelia Mee from 1859, discussed here.)
Thérèse de Dillmont clarifies the relationship between posts as used in closed and openwork, in the Encylopedia of Needlework initially published in 1886. The terminology in it is an amalgam of earlier English nomenclature and her native German. For example, the definition of treble crochet describes it as a “little column.” This is taken directly from the corresponding definition in the German edition which, unlike the English one, also makes a categorical distinction between stitches and posts. In openwork the posts are “set between those of the preceding row.”
The German caption translates to “Triple and Quadruple Posts.” The alternative “Extra Long Stitch” only appears in the English one, ambiguously applying that label to posts of the two different heights. In fact, Dillmont uses “treble” both in the expected sense and as a general designation for a post of any height, just as the corresponding German term does.
The staggered vertical alignment of the posts seen above is effected by inserting the hook under both legs of the chain loop. In closed work the posts are made “directly above one another” by inserting the hook into the chain loop at the top of the post to which the new one is being anchored, now termed “back loop only” (BLO).
The vertical separation between the horizontal chains in both forms varies with the height of the post, but adjacent posts are only interlooped at one point. However, Dillmont also describes a technique for joining vertically aligned wales along their entire length.
Connected trebles — Trebles, connected together, can be worked to and fro, and take the place of plain stitches. Begin with a chain, then make a treble [i.e. post] of the required height, form as many loops as you made overs for the treble, take up the upper thread of the stitch nearest the treble, turn the thread round the needle, bring it back to the right side and draw the needle through the trebles, two at a time.
The German caption translates to “Interlaced Posts” and the procedure remains familiar in what are referred to as linked posts, again of any height. This is a warp-based technique that effectively turns the simple Tunisian crochet stitch (TSS) at right angles to its customary orientation.
If the basic TSS is conceptualized as weft crochet, its vertical transform is no less an instantiation of warp crochet. The most common Victorian name for this structure was “tricot,” borrowed from the French word for knitting. It is a hybrid of knitting and crochet, and can be described entirely in terms of either. If treated as knitting, a linked post is a warp-knitted construct.
The 1 January 1864 issue of the German periodical Der Bazar (on which Dillmont relied heavily and where the first known tutorial illustration of the TSS appeared in January 1858) describes and illustrates another Tunisian crochet stitch that builds particularly dense fabric entirely along the warp by replacing the vertically chained component of a post with a single loop.
Spiral Post Stitch [Spiral-Stäbchenstich]
“This crochet stitch, a very original variation of the Tunisian stitch, forms an unusually thick and heavy fabric and is therefore most particularly suited to making travel or sled blankets. It can additionally be used for small foot covers or warmers, and also worked in bands with strips of plush or angora, assembled into blankets. Illustration no. 9 [above] shows the crochet stitch done with 10 ply wool carpet yarn, selected either in 3—4 shaded nuances or in 2 markedly contrasting colors. In the first case an entire pattern row is worked in each nuance, in the latter case wide and narrow bands can also be alternated. If it is a question of predominant taste and fashionability, this would dictate an arrangement of blue and green bands, or a colorful sequence of bands as a Scottish plaid, so to speak.
Make a very loose foundation and work back along it:
The 1st pass of the 1st pattern row. Wrap the thread around the needle as if making a post stitch, but 5 times. Insert [the needle] into the 4th stitch of the foundation, skipping 3 stitches, which also forms the first post. Pull a loop through the foundation stitch, wrap the thread around the needle once again and pull it through the loop just formed and the entire coil that is on the needle, but not through the loop behind it. This leaves 2 stitches on the needle. Wrap around it another 5 times and work another spiral post of the same type into the following stitch of the foundation, as just described — repeat in each of the remaining foundation stitches. The loops pulled through the coils always remain on the needle as with the Tunisian crochet stitch.
The 2nd pass is worked backwards from left to right, as with the Tunisian crochet stitch, closing the stitches on the needle one by one.
This completes the 1st pattern row. The following pattern rows are worked in exactly the same way. However, after the 5-fold wrap around the needle, always insert it not just into the vertical loop at the top of the stitch in the previous row but also into horizontal loop lying behind it. The incomplete top row in the illustration shows the two loops through which the new loop should be pulled, aligned on a small arrow, and also otherwise gives a very clear understanding of how the work is conducted.”
This structure has no weft-based correlate since a chain is required to return the free end of the working element to the starting selvage. However, it can also be produced in ordinary crochet. Dillmont presents it as a “bullion stitch,” showing a shorter form with the five-wrap coil and a taller form that can be wrapped up to twelve times.