Knit Stitch vs Purl: One Loop, Seen From Opposite Sides

Turn a scarf of plain knitting over and the smooth Vs become rows of bumps. Nothing about the yarn has changed. Only the side being looked at has, and that is the whole difference between the two stitches.

What is a knit stitch?

De Dillmont calls the knit stitch plain stitch and names it “the easiest stitch and the first which a knitter has to learn” (fig. 349). In her instructions, the right-hand needle goes into the first loop on the left-hand needle, from below, under the front of the loop. The yarn is laid under that needle and drawn through as a new loop, and then the old loop drops off the left-hand needle.

So a knit stitch is a new loop pulled through an old one. Nothing is tied, and the loop below stays in place only because the new loop passes through it. Cord can also be built from strands without any loops or knots, by crossing them over and under one another, as kumihimo braids are.

Which side is the right side? De Dillmont says plain knitting is used “wherever a perfectly smooth, even surface is required.” She adds that it “looks quite differently on the wrong side” from the right side, where it shows “vertical rows of plaiting.” This page reads those vertical rows of plaiting as the columns of Vs, so the side covered in Vs is the right side.

Purl: the same loop from the back

“You may intentionally knit the wrong side of plain knitting,” de Dillmont writes. “This is called purling.” She also calls the purl the back stitch or seam-stitch (fig. 350). It is not a new kind of loop but the knit loop itself, made so that its back faces the knitter.

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Look at where the strands cross. From the front, each loop's two legs lie over the head of the loop below and over the yarn connecting neighboring stitches, which is why the front shows legs standing as Vs. From the back, every one of those crossings is reversed, so the heads and the connecting arcs lie on top and read as horizontal bumps.

Hitomezashi sashiko is another stitch structure that only makes sense once both faces have been examined.

Which way the new loop is drawn

De Dillmont's two sets of instructions differ in where the yarn is laid and where the needle enters, and this page reads them as one motion pointed in opposite directions. In plain stitch the needle enters from below, and the new loop comes out toward the knitter. In purl the yarn is laid over the left needle first, and the needle enters from above, behind the yarn, and the new loop is then drawn out through the back.

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She gives the purl two jobs: it is “used in knitting patterns, and for marking horizontal lines in smooth surfaces, such as the seam of a stocking.” A line of purls on the front is a line of knit stitches turned to face the opposite direction.

How it fails: a dropped stitch runs down

Below the needle, each loop is held by one thing: the loop drawn through it from the row above. Every loop signs for the one below it, but only while a loop above passes through. If a live loop slips off the needle, nothing passes through it. Once the fabric is stretched, that loop can open, which releases the loop below, and so on down the column.

That run is this page's reading of the loop structure, not a line from de Dillmont, though her book supports it indirectly. Stitches are cast off at the end “to prevent the stitches from unravelling,” and to mend plain knitting, loops are cleared “by ravelling them out top and bottom” (fig. 368).

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Her fig. 387 even builds a decorative pattern on dropping: its “Knitting pattern with dropped stitches” drops both of its double overs and one stitch on purpose, then takes the dropped stitch up again and knits it. A column of purls could run the same way, since a purl is the identical loop. Which layer was checked explains what these schematics do and do not claim.