Deep Dive Details on ICDD vs. Standard CDD (aka s2kp)

September 24, 2022

Deep Dive Details on ICDD vs. Standard CDD (aka s2kp)

Inverted Central Double Decrease: Why did I use it when there are so many existing double decreases already = CDD aka s2kp, sk2p, k3tog, p3tog, sssk, k3tog tbl... ? You'd think I could make life easy and settle for 'close enough'. LOL. Not me!

I came up with it while designing my Dragon Scales Stitch

Ravelry Dragon Stitch Pattern Bundle. Payhip Dragon Pattern Bundle

For these Scales the purl side is the public side, but for an easier knitting experience, the knit side is referred to and worked as the RS. That means on the projects done in the round, all “work” is done on the knit side and then the items are turned inside out when finished.

While prototyping the Scales stitch I found the CDD worked so-so. It had a rigid center line on the back, which also tended to veer off to the right and did not lay quite how I wanted on the purl side. I wanted something that kept the center stitch in the center, except tucked under/ at the bottom of the stack = A purl side ridge that was not raised. I fiddled until I got what I eventually called an ICDD.

How exactly does my ICDD differ from a standard CDD (aka s2kp)?

First, how are they alike? They are both double decreases taking 3 stitches into 1, and both keep the center stitch at the center.

The difference is in the Stacking order and an ICDD is not simply the WS of a CDD.

Note: Since I often use it as a WS (purl facing) stitch, to avoid confusion, I'm going to refer to knit side and purl side, not RS/WS, in the explanations below.

Let’s start with details of the CDD

A Standard CDD (aka s2kp) makes a raised ridge on the knit side with the center stitch at the top of the stack, as shown above.

The purl side has a sharp angle of join, and as more are added above it the ridge tends to curve right.

Standard CDD Construction:

The 3 stitches start as 1, 2, 3 and get re-ordered and stacked as 2, 1, 3. Viewed from the knit side the Center stitch (2) is on *top* of the stack.

Knit Side: Slip first and second stitches together as if to knit. Knit 1 stitch. Pass two slipped stitches over the knit stitch. (s2kp)

Purl Side: Slip first and second stitches together as it to purl through the back loop. Purl 1 stitch. Pass two slipped stitches over the purl stitch.

Now compare the ICDD

My ICDD does not make a raised ridge on either side. Instead, it has a purl side recessed ridge that tends to stay vertical and not curve.

ICDD Construction:

The 3 stitches start 1, 2, 3, and get re-ordered and stacked as 3, 1, 2. Viewed from the knit side the Center stitch (2) is at the *bottom* of the stack.

Knit Side: slip 1 knitwise, slip 1 knitwise, knit the 2 slipped stitches together through back loops, return stitch to LHN, pass 2nd stitch to Left over 1st and off needle, slip stitch purlwise to RHN.

Purl Side: slip 1 purlwise with yarn in front and keeping yarn at front through rest of construction; slip 1 knitwise, slip 1 knitwise, return 2 stitches to LHN, purl these 2 stitches together through back loops, pass 2nd stitch to Right on RHN over 1st and off needle.

Seeing it worked is sometimes more helpful than words so, pasted from the Patterns is:

Special Stitch Constructions Section + Links to Video Demonstrations.

Inverted (aka Reversed) Central Double Decreases: This special stitch creates a recessed purl side central double decrease. (The Center Stitch remains in center but underneath side “Arms”)

ICDD = Inverted Central Double Decrease (RS) = slip 1 knitwise, slip 1 knitwise, knit the 2 slipped stitches together through back loops, return stitch to LHN, pass 2nd stitch to Left over 1st and off needle, slip stitch purlwise to RHN. Decreases 3 stitches to 1 and maintains placement of the center stitch.

Demonstration of ICDD - https://youtu.be/RkNSWKfS8Kk

ICDDp (WS) = Inverted Central Double Decrease Purl (for WS of work) = slip 1 purlwise with yarn in front and keeping yarn at front through rest of construction; slip 1 knitwise, slip 1 knitwise, return 2 stitches to LHN, purl these 2 stitches together through back loops, pass 2nd stitch to Right on RHN over 1st and off needle. Decreases 3 stitches to 1 and maintains placement of the center stitch.

Demonstration of ICDDp (WS) - https://youtu.be/YNjROXQelvc

Some New Dragon Scales Patterns: