Horizontal fold lines in knitting, part 1: knit sides out, purl sides in the fold

Just as the universe folds and twists in accordance with laws of interest to physicists, so knitting curls and folds in accordance with laws of interest to handknitters.  For example, the tendency of stockinette to curl purl side out is well-known and many excellent knitting designs take this into account, working with the roll, rather than going all out to conquer it.  Perhaps less well-known is an equally strong force of knitting, which can equally add a structural design element: the tendency of stockinette to fold along a purled row.

purl-line on the knit face of stockinette, unfolded (left) and folded (right)

Specifically, when you want knitting to fold back on itself along the row-line, such as at a hem or cuff, it's easy to make the fabric fold sharply by running a row of purl on a stockinette background.  This strongly forces a stockinette fabric to fold in half with the knit sides out while the purl sides are trapped in the fold, back-to-back, as shown in the photo above.

HOW-TO

flat knitting

If knitting stockinette back and forth, you simply knit on the purl side for one row, then return to pattern.  This means that you will work 3 rows of knit successively and the center of these three--the one that looks like a purl line, but is located on the smooth knit side of the fabric--will be the fold line.

circular knitting

If you are working in the round, it's a little different.  As you know, when knitting stockinette circularly you're always working on the knit side, so you'll simply purl a single round to get the same effect.

This is all very simple, but there is one little wrinkle to getting a neat fold line when knitting circularly.  As you know, however, knitting in the round creates a spiral.  This means that the beginning of each round is stacked above and one stitch over from the end of the previous round.  In the context of a fold line, this means that the beginning and end of the purl round "jog," they won't line up because they aren't actually in the same round at all. The discontinuous purl line is highlighted in pink in the photo below.

discontinuous purl line "jog" when worked in the round

To avoid this "jog," use the same trick as for avoiding color jogs:

• work the entire purl round as usual.  
• on the next round, where you would set off knitting in the ordinary course of things, simply SLIP the FIRST purl stitch you worked instead.  In other words, at the end of the purl round, instead of working a knit stitch as the first stitch of the next (knit) round, simply slip the next stitch on your needle INSTEAD of knitting it. 
• All further rounds are worked normally, and this is the only stitch slipped.  

This slipping trick drags up some stitches and squishes others, aligning the beginning and end of the purl round, and essentially eliminating the jog.  As seen in the photo below, the resulting purl line, highlighted in pink, is waaay better than the jogging line of purl in the photo above.

discontinuous "jog" alleviated by slip-stitch method above

In sum so far: the introduction of a purl row/round on a stockinette ground will cause the fabric to to fold very sharply along the purl row, knit side out and with the purl side of the fabric trapped inside the fold.

VARIATIONS ON A THEME

As with many things knitting, there are some neat variations.

beefier fold line

For a beefier thicker fold very suitable to utility wear, consider a double purl-line fold.  Although this looks like (and is!) the surface decoration called "welting" when seen on unfolded stockinette, if you fold the fabric at this welt-line you will find you've created a thick, pleasant, sturdy edge--much more substantial than a single purl-line fold line, and very suitable to outerwear or rough use or heavy yarns.

beefier double purl-line (aka "welting"), unfolded (left) and folded (right)

contrast-colored fold line, method 1

There are two ways to make a contrast colored fold line, a gold fold line on a green fabric, for example.  The classic method is done in three steps:

• On the row or round BEFORE where the fold is wanted, work a row or round in contrast color, but keep to your stockinette pattern (knit if in the round, purl if working back and forth)
• On the row or round where the fold is wanted, return to the main color and purl
• On all following rows/rounds, return to the ordinary pattern of the stockinette fabric

contrast-colored method 1, unfolded (left) and folded (right)

When folded, this single line of contrast color yields a fold with a pleasant "stitched" sort of appearance--the main color (green) shows in little dots below the gold contrast color fold, per the above illustration.

contrast-colored fold line, method 2

For a more consistent-colored fold line (no "stitched" appearance) two rows or rounds are worked in the contrast color, as follows:

• On the row or round BEFORE where the fold is wanted, work a row or round in contrast color, but keep to your stockinette pattern (knit if in the round, purl if working back and forth)
• On the row where the fold is wanted, remain in the contrast color and purl a row or round
• On all following rows or rounds, return to the main color, and work in the ordinary pattern of the stockinette fabric

contrast colored method 2, unfolded (left) and folded (right)

Note--although two lines of contrast color have been worked, this is nonetheless a single purl-line fold, because only one row has been purled.  If you wanted to combine the beefy double-purl line fold with the contrasting color trick, you'd have to work THREE lines of color and two lines of purl.

* * *

This is the first post in a two part series about horizontal folds in knitting.  The next post will be about getting stockinette fabric to fold the other way, so that the PURL (reverse stockinette) sides are out, with the KNIT sides trapped in the fold, back-to-back.

Until then, good knitting
--TK
PS: Why yes, I am from Wisconsin.  Did my green and gold color scheme give it away?