Ariel's craft journal (dragoncrafter) wrote in knitting,

Double decreases and decreases from the purl side

A while ago I wrote up everything I knew about single and double decreases, particularly about how to do them on the wrong side, and posted it to dragoncrafter, planning to post it here sometime when I had pictures. Then yesterday, flybystardancer posted asking about centered double decreases, and I remembered that I had pictures, so I thought I'd post it.

I knitted Leaves in Relief inside-out. This is a complicated pattern that includes lace leaves. Consequently, I had to spend a lot of time thinking about how to create something that will look like a sl 1-k2tog-psso from the right side, while working from the wrong side.

Today¹ I was reading this post on String or Nothing. (She was doing a series on how to chart things, which I highly recommend.)

In the middle of it, I came across the following phrase:

Again referring to the Sainted Barbara, we see that a s1-k2tog-psso done on the right side has as its wrong-side counterpart the delightfully awkward p3tog through the back of the loop.
This bothered me quite a bit, because it's not accurate.

This provoked me to finally get around to writing up how to produce any of the single or double decreases from the wrong side.

Single decreases

  • There's only one good way² to get a right-slanting single decrease while working from the right side: k2tog (knit 2 together).

  • However, if you want to do a decrease on the wrong side that will look like a k2tog from the right side, you have three options.

    First, there's the fast efficient easy decrease: p2tog. It's the one that's usually used. Yes, purling 2 together through the front loop is the wrong-side substitute for knitting 2 together through the front loop, and purling 2 together through the back loop is the wrong-side equivalent of knitting 2 together through the back loop. This is because working through the front loop always puts the left-hand stitch on top, and working through the back loop always puts the right-hand stitch on top. Now, when you turn fabric over, the top stitch becomes the bottom stitch, and the left stitch becomes the right stitch. These two effects cancel out; so if the left stitch is on top on the wrong side, then the left stitch will be on top on the right side as well.

    Next, there's the slower SSP tfl: slip two as if to purl, insert left needle in both slipped stitches, and purl. (I used to think that this was completely pointless, but I have since discovered that it is useful if you knit combined, and in a few other weird situations. However, usually I prefer a simple p2tog.)

    Finally, you can "slip 1 purlwise, purl 1, pass slipped stitch over". Some people think this is easier than p2tog.

    Any of these three options will produce a stitch that, when the fabric is turned around, looks like a k2tog.

  • There are three ways to make a left-slanting single decrease from the right side. There's the SSK,³ SKP (slip 1 knitwise-knit 1-pass slipped stitch over), and then there's the k2tog tbl (knit 2 together through back loop). The SSK is considered (by many people) to be the best-looking choice. Some people think that the SKP is easier. K2tog tbl is probably the fastest if you're good at it, but it twists all the stitches, and is kind of hard for tight knitters.

    I suggest looking at this page; she has examples of all three kinds of left-slanting right-side decrease, plus a picture of the SSP tbl.

  • However, there are fewer options for doing this on the wrong side: the obvious purl analogs of SSK and SKP produce things that slant to the right.

    P2tog tbl (purl two together through back loop) is a lot like k2tog tbl. It produces twisted stitches, it's tricky if you're a tight knitter at all, and it slants to the left when viewed from the right side.

    My favorite choice for left-slanting decreases worked from the wrong side: SSP tbl. This goes "slip 2 knitwise and insert left needle, as if to SSK, and remove right needle. P2tog tbl." Unlike a standard p2tog tbl, it does not twist the stitches, which looks better, and is also easier to work, because untwisted stitches are not as tight.

    This is often but not always, just called an SSP. Some extremely silly people use SSP to refer to what I call a SSP tfl, so I use SSP tbl to refer to the left-slanting wrong-side decrease to avoid confusion.

    There is also an unnamed (and very slow) decrease: Purl 1, slip 1 knitwise, return the slipped stitch and the purled stitch to the left-hand needle, pass 2nd stitch over the first one, and slip back to the right-hand needle (purlwise). This should produce untwisted stitches, just like SSP tbl, but is slower (and potentially sloppier.)

Some people have issues with their decrease tension. In a decrease, you're often pulling harder with your needles on the stitches than you would be if you were just knitting. This means that the two loops being decreased want to grow.

The first (rightmost) loop often does, by pulling a little bit of yarn out of the stitch just worked. This stitch is hanging below the right needle, with nothing in it but another loop of yarn; it can shrink easily.

The second loop, however, can't pull any yarn to itself. On each side, it's got a stitch which still has a needle in it. These loops can't shrink, so they can't give up yarn, so the second loop can't grow.

In addition to this effect, when you insert the needle into the stitch after the decrease, it does want to grow a little bit. It does this by pulling yarn from the stitch just worked, thus causing the second loop (in the decrease) to tighten up and look neat.

Thus, decreases where the second loop ends up on top (k2tog, SSP tbl, or p2tog tbl) often look neater than decreases where the first loop ends up on top (SSK, SKP, k2tog tbl, and p2tog). This should be the only difference in appearance between, say, a k2tog on the right side and a p2tog on the wrong side.

To compensate for this, some people advocate doing SSK as "slip 1 as to knit, slip 1 as to purl, insert left needle, knit 2 together." This twists the bottom (mostly invisible) loop, which tightens up the top loop. I don't do this, and whenever I say "do something as if to SSK" in this post, I mean slipping all stitches knitwise.

Double decreases

A double decrease consists of stacking three loops and pulling a single loop through them, thus decreasing two stitches away.

Ignoring issues of tension, double decreases can be completely described by (1) the order of the three stitches, and (2) whether the stitches end up twisted. I'm going to look just at the issue of order, and treat twisted kinds as variants. This is like considering k2tog tbl as another way to make something that looks like an SSK. There are, mathematically, six possible orders: Image hosted by Photobucket.com

  • Left-center-right (LCR). This puts the left loop on top and the right loop on the bottom. It's made by knitting 3 together (k3tog). It slants very strongly to the right.

  • Right-center-left (RCL). This can be done as SSSK, S2-k-p2sso, or k3tog tbl. That is, you do what you would do for a left-slanting single decrease, but do it with one more stitch. It slants very strongly to the left. k3tog tbl, like most tbl stitches, twists the stitches and the others do not.

  • Center-right-left or center-left-right (C**). These decreases put the center stitch on top. Consequently, they look more symmetric than any of the other double decreases. CRL is usually done by working *slip 2 as if to k2tog, knit 1, pass 2 slipped sts over.* You need either a magnifying glass, bulky yarn, or to be looking really really closely to tell the difference between CRL and CLR, so I'm going to treat them as identical. C** means "either CRL or CLR". This decrease doesn't slant at all. It is the decrease running up the middle of Branching out.

  • Right-left-center (RLC). This is usually done by working *slip 1, k2tog, psso.* alunissage has an alternative method: Slip 1 as if to knit, slip 2 as if to k2tog, insert left needle from left to right through all three stitches and knit 3 together, as if to SSSK.

    On the right side, this is probably the easiest of the double decreases. This decrease sort of slants to the left. In some patterns, it's used that way, and you can use it to replace RCL, and you can pair it with LCR to get symmetric double decreases.

    However, this decrease also looks sort of like an inverted V. This is what is used at the tops of, say, leaves. (See the tree article for closeups of leaves to show you what I mean.) If you use it this way, it looks fairly symmetric, and you don't really want to replace it with RCL. This is my problem with Walker; by replacing it on the wrong side with "p3tog tbl", you get an RCL instead of an RLC, which is definitely a left-slanting decrease and not a centered one.

  • Left-right-center (LRC). This is the actual mirror image of RLC. It's kind of rare to do this from the right side. Either it's being used as a right-slanting decrease, in which case LCR (k3tog) is a lot faster, or it's being used as a symmetric V-shaped decrease, in which case RLC is easier. It's used in Leaves and Waves, but I think in that case it could be replaced by LCR. If you really want LRC, the Leaves and Waves method is: SSK, slip the just-knitted stitch to left needle purlwise, pass next stitch over, and slip back to right needle, again purlwise.

    Again, alunissage has an alternative method: slip 2 knitwise as if to SSK, then insert left needle through both stitches from right to left (this is sort of like slipping as to k2tog), then knit 3 together.

So those are the five possible decreases. Here's how you do them on the purl side:
  • LCR: p3tog or sl 2 purlwise-p1-p2sso.

  • RCL: sssp tbl. Or p3tog tbl, if you don't mind twisted stitches and are a loose enough knitter to be able to do it.

  • C**: I don't think I've ever actually done this one. I'd suggest: slip 2 as if to SSK, insert left needle through both stitches from right to left, then remove right needle and p3tog. This produces CLR, incidentally, not CRL.

  • LRC: Slip 1 purlwise. Work SSP tbl (or p2tog tbl). Pass slipped stitch over. This is a bit slower than the right-side version of RLC, but not by too overly much.

  • RLC: If possible, don't. If you want the effect of a left-slanting decrease, use RCL. (See, here's what Walker was thinking of.) If you want the effect of a centered, inverted-V decrease, use LRC. Deciding which is a judgement call that has to be made in every pattern, so it's kind of hard to put in a nice neat table of decreases.

    If you must do RLC, you can borrow the moves from LRC for the right side: SSP tbl, slip the just-created stitch to left needle purlwise, pass next stitch over, slip back to right needle, again purlwise. This will, sadly, twist the last stitch, which is the one that ends up on top and is most visible.

There are also larger decreases out there-for example, the ones used to close off cables in closed-loop cabling. I'm not going to go into those, because they tend to be explained wherever they come up.
¹ Where by "today" I mean "November 6, 2005".

² Unless you're left-handed or you knit Combined. If you knit Combined, working decreases on the right (knit) side is harder because all the stitches are set up facing the wrong way. However, working on the decreases from the wrong side is exactly as I've described here.

If you're left-handed, then note that the moves I describe to produce a left-slanting decrease will produce a right-slanting decrease for you. How you integrate this into your own patterns, I leave to your judgement.

³ If you don't know what an SSK is, go to stitchguide.com or knittinghelp.com and find out. It's kind of hard to explain, and a lot of this won't make sense if you can't do it.

Tags: technique - increase/decrease
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