December 30, 2008

Increases and decreases

Posted in math, stitches at 7:01 pm by Pink

For my own (and other knitters’) reference:

So, as most of you have probably figured out, purling is literally the same thing as knitting, just from the “wrong” side. (You can, in fact, just learn to knit with the needles opposite–not quite the same as knitting left-handed–and never need to turn your work.)

In order to get that smooth “v” stitch that everyone thinks of when they think of knit, you actually need to alternate rows of knits and purls (assuming you’re doing this flat). So a knit/purl combo (and I’m talking a knit row then a purl row, not a knit stitch next to a purl stitch) is essentially (or is, really) a bunch of intertwined loops–knit pulls the loop up from the back, and purl pulls the loop up from the front, so if you do one on each side, the loop gets pulled all one one side and is nice and smooth like one usually thinks of knitting.

Since knitting is done down one row and then back along that same row–and, sorry lefties, but we’re assuming that we’re right-handed here for the moment (your yarn hand doesn’t matter–if it’s in your left hand that’s Continental/German, right hand is English/American, the needle that is doing the “active” knitting is always the right one)–decreasing stitches, since you’re eliminating one, are going to slant. They just are, it’s part of their nature. Since stitches are moved from the left needle to the right needle, if you decrease by doing a straight up knit-two-stitches-together (K2tog), you’re going to end up with a stitch that slants to the right, since you’re coming from the left and pulling the loop towards the right.

Now, to REPLICATE that stitch on the “wrong” side–the purl side of stockinette–it’s easy to know what to do. You purl-two-stitches-together (P2tog), since purl is the same as knit and you’re going the opposite direction so it ends up. Purl decreases are weird, because they slant one way as you watch, but appear on the “right” side the opposite way since they’re just knitting backwards.

So what I’m trying to say is a K2tog = P2tog, and you get the same thing–it’s fabulous and looks lovely and they match up quite well. These are your most basic decreases. If you’re doing it in the middle of a piece, it doesn’t matter too much–if you’re decreasing on edges, though, it gets really obvious and really important really fast.

So, K2Tog and P2Tog slant to the right. Awesomesauce! The obvious question is this: how do we slant to the left?

For knitting, there are a number of options–the most standard is SSK, which is slip two stitches as if two knit, then pop the left needle in front of those stitches and knit through the back loop. (I prefer SSK-improved, which is the same, except for the second slipped stitch you slip purlwise. It lies a little flatter.)

Now, how does one replicate this on the purl side? The literal answer is that since we want to do the purl/backwards version of a SSK, we want to PSS–which would be purl, then… slip two stitches with… absolutely no consequence. It doesn’t work. All you’re doing at that point is passing stitches back and forth and not decreasing at all. You can purl 2 together through the back loop, but that twists the yarn and it gets fucked up and messy and I don’t like it as a match for SSK since, well… it just doesn’t match!

In my anal retentive quest for symmetry and obsession with topology as it relates to pretty fiber, I went in search of its match: and, through the wonders of Google and LJ, I found it!

The match to SSK is SSP tbl–slip slip purl through back loop. Slip two stitches knitwise, insert left needle as if to SSK, remove right needle, then purl those two stitches through the back loop. Since we slipped them first, it twists them correctly, and we get a stunning opposite. WHOO! GO Dragoncrafter

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