Three Ways to Knit Centered Double Decrease Purlwise (CDDp)

Some decreases lean to the right; some decreases lean to the left. Centered decreases, as the name suggests, don't lean either way. They are centered in that the decrease rises straight upwards.

I've written about centered double decreases before. In my blog post Smooth Moves: Improving SSK, SSSK, and CDD Decreases I showed two ways to work a CDD, as its abbreviated: the conventional way and a smoother way with fewer movements. Both methods work the decrease in stockinette on the right side of the work. But what if you have to mirror the decrease on the wrong (reverse stockinette) side of the work, like in the Chamomile Dreams shawl or the just-released Rockweed cardigan pattern? That's where CDDp comes in.

In this blog post I'll demonstrate three ways of knitting a centered double decrease on the purl side of the work. One of them is based on a purl three together (P3tog) decrease, typically a right-leaning decrease. The other two are based on passing slipped stitches over (PSSO) which is normally a left-leaning decrease.

When looked at from the stockinette side of the work, all three methods produce decreases that are indistinguishable in looks from the ones worked on the right side — and from each other! Compared to a right-side CDD, though, neither method produces structurally an exact match.

Let's get CDDp-ing!

Method #1: P3tog-based

This method is based on a P3tog decrease and it's the one demonstrated by Suzanne Bryan on her video.

1. Work to one stitch before the center line of the decrease. The three stitches over which the decrease is worked are next on the holding needle. This can be difficult to see on the wrong side so take a peek to the right side of the work to confirm you're in the right spot.

2. Move the working yarn to the front (wrong side) of the work.

3. With yarn in front, slip the first stitch knitwise, reversing the stitch mount.

4. Do the same to the second stitch (that is, sl1 knitwise wyif).

5. Insert the holding needle into the two slipped stitches from right to left, restoring stitch mount but reversing stitch order. The two stitches swap places.

6. Finally, purl the next three stitches together. Give the working yarn a little tug to make the stitch nice and snug.

Looking at the decrease from the right side of the work, the right-most stitch is on the bottom, the left-most stitch is in the middle of the CDDp sandwich, and the center stitch is on top. This is structurally slightly different to a CDD worked on the right side in which the right-most stitch is in the middle and the left stitch on the bottom. But can you tell the difference?

Using the P3tog-based method I tend to get these little protruding loops peeking under the central decrease line. But that might just be my tension.

Method #2: PSSO-based

The second method of doing a CDDp is the one I prefer but it might be a little trickier to execute. This one is based on a PSSO or "pass slipped stitches over" decrease.

1. This method starts exactly the same: work to one stitch before the center line of the decrease.

2. As before, move the working yarn to the front.

3. This is the most awkward bit of the decrease! With yarn in front, insert the working needle into the backs of next two stitches as if to purl together through the back loops, that is, going from left to right.

4. Purl the next (third) stitch.

5. Pass the two slipped stitches over the stitch you just purled. Give the working yarn a little tug to neaten the work.

Here's a finished CDDp decrease done using the PSSO-based method. Looking at the decrease from the right side of the work, the stitches fall in the same places as in the first method: the right-most stitch is on the bottom, the left-most stitch is in the middle, and the center stitch is on top.

If you look really carefully behind the center stitch, though, you'll notice that the left-most stitch is now twisted at its base. You might need to examine the work with a magnifying glass to see that the center stitch is also twisted. For some weird reason it just doesn't appear to be! (I suspect this has something to do with being connected to a twisted stitch on one side and an untwisted stitch on the other side.) In my opinion, this method gives the CDDp is slightly neater look than the P3tog-based method without the protruding loops.

Method #3: SSPP2

The last method combines the two approaches: re-orienting the stitches as in method #1 and passing slipped stitches over as in method #2. Interweave call this decrease SSPP2 which, I presume, stands for "slip, slip, purl, pass two". But there's a lot more going on between the "slip" and the "purl".

1. Again, work to one stitch before the center line of the decrease.

2. With yarn in front, slip two stitches knitwise one at a time (like in method #1).

3. Return the stitches to the holding needle in their new orientation.

4. Still with yarn in front, insert the working needle into the backs of the next two stitches as if to purl together through the back loops (like in method #2). Stitch mount is restored but the two stitches swap places.

5. The rest is a carbon copy of method #2: purl the next stitch.

6. Pass the two slipped stitches over the stitch you just purled.

Here's a finished SSPP2 decrease.

Structurally this decrease is equivalent to the two methods above: the right-most stitch (green) is on the bottom, the left-most stitch (teal) is in the middle, and the center stitch (red) is on top. What's the advantage then? I don't know! To me the SSPP2 method seems like an overly convoluted way of achieving the same result as the two other methods.

The differences in the three CDDp variations are minor and, even comparing side by side, it's really hard to tell them apart. Try them out to see which one you like best!

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