Monday, October 12, 2009

Purl decreases: p2tog, p2tbl, ssp

The same way there are two versions of knit decreases, there are also two versions of purl decreases: the right-leaning and the left-leaning.

*A purled decrease which slants RIGHT as seen from the front side of a stockinette fabric is not usually called a "right leaning purled decrease." Instead, the decrease is named by its method of creation. In other words, these right leaning decreases are usually called "purl 2 together" (usually abbreviated "p2tog") because that's what you do to get them.

*A purled decrease which slants LEFT as seen from the front is called various things, but hardly ever simply "left leaning purled decreases." Instead, like the right-leaners, these left-leaners are also usually named for their method of making. So, just to confuse the heck out of you, these left-leaners are sometimes also called "p2tog," just like the right leaning ones. Other, more common names include "slip, slip, purl" ("ssp") or "purl 2 together through the back loops" (usually abbreviated "p2tbl" but sometimes "p2togtbl.")

RIGHT LEANING (as seen from the front)

This is a simple one step process: Instead of sticking your right needle into the first (green) stitch at the tip of the left needle and purling it, you instead stick your right needle into the first two stitches (green and blue) and purl them together, as shown below.

The result, as seen from the front, is shown below.

Do you see what you've done? By first inserting your right needle into the first stitch on the tip of the left needle (the green stitch) and next into the second stitch on the left needle (the blue) you have forced the green stitch in front of the blue stitch, as seen from the front (knit side) of the fabric. The green stitch has "eaten" the blue stitch to its right thus pulling the green stitch rightwards ---> over the blue stitch, and this is what forces the decrease to slant right. The slant is not purely rightwards, however, but "up and to the right" because the base of the stitches remains separated--it is only the heads which you've merged. As stated earlier, these right leaning decreases are usually called "p2tog."

LEFT LEANING (as seen from the front)

This is a three step process

Step 1: Slip the first (green) stitch on the tip of the left needle onto the right needle KNITWISE. This means to insert the needle into the stitch as if you were going to knit it. When the right needle is inserted this way and then the stitch slipped off, the stitch turns away from its usual right-arm-forward orientation. Now, the left arm of the stitch is forward (towards you) and the right arm is back (away from you.) Note that you do not pass a yarn through this loop, you just slip it from the left needle onto the right one, changing its orientation along the way.

Repeat this process with the next (blue) stitch on the tip of the left needle. You will wind up with both the blue and the green stitches on your right needle, and both should be laying left arm forward as shown by the red arrows.

Step 2: Return the blue and green stitches to the left needle without disturbing their orientation. The end result of all this slipping and sliding should be the blue and the green stitch laying on the tip of the left needle, oriented left arms forward, right arms back.

Once these stitches are parked on the left needle, you will insert the tip of the right needle into the right (back) arms of both of these stitches as shown by the red arrow. Note that the right needle is to insert from the back, first under the right arm of the BLUE stitch, and then under the right arm of the green stitch. This is admittedly a bit awkward, but persevere.

Step 3: Again: once your right needle has followed the path of the red arrow, it will have been inserted first through the right (back) arm of the second stitch on the left needle (the blue stitch) and next through the right (back) arm of the first stitch on the left needle (the green stitch) as shown. Note also that the running yarn has been brought to the front before the right needle is inserted, in order to make it possible to purl.

Once you draw the running yarn through these two loops, the result, as seen from the front, is as below.

The loop through which the needle was first inserted, here the blue one, has been forced to the front. This blue stitch has "eaten" the green one to its left, which pulls the blue stitch <---- leftwards over the green stitch, so the decrease slants to the left. The slant is not purely leftwards, but rather "up and to the left" because with this decrease, as with the previous one, the base of the two stitches remain separated, it's only the heads which you've merged.

As stated earlier, this left leaning decrease is sometimes called "p2tog" just like the right leaning decrease is. However, it is more commonly called "slip, slip, purl" (ssp) or sometimes "purl 2 together through the back loops," (p2togtbl or p2tbl).

You can straighten out any confusion about the messy naming situation of purled decreases by simply ignoring the names given in your pattern. Instead, look to see which way the decrease OUGHT to lean for best looks, and do that. Remember the rule:

*if you first insert your right needle through the FIRST (green) stitch on the left needle tip and then through the second (blue) stitch, the green will be pulled rightwards ----> over its neighbor and the resulting decrease will slant right as seen from the front of a stockinette fabric

*after the re-orientation steps (in other words, when you get to step 3) then if you first insert your right needle through the SECOND (blue) stitch on the left needle tip and then through the first (green) stitch, the blue will be pulled <---- leftwards over its neighbor and the resulting decrease will slant left as seen from the front of a stockinette fabric.

Two last notes:
1. Some instructions for a left leaning purled decrease ignore the re-orientation steps (steps 1 and 2) and instead jump directly to purling through the back loops (step 3). The result is a twisted loop on the front surface of the fabric--not so pretty.

2. If your decreases are to be viewed from the purled side of a stockinette fabric (reverse stockinette side) then it really makes absolutely no difference how you make them, so make the one-step right leaning decreases because they are easier and quicker. The reason it makes no difference is because in the purled and bumpy landscape of a reverse stockinette fabric, the orientation of the loops will simply not show. As long as you're making the purled decreases where you ought to be (on the side of the marker as specified by your pattern) you'll get the result envisioned by the designer. It's only when viewed from the persnickety and smooth front (knit) side of a stockinette fabric that the direction of lean is important.


Addendum, added 10-13-09. In the comments, Rachmouse asks for a photo of these purl decreases from the purl side. Here you go Rachmouse!

But...just one thing, first. Also in the comments, Cheryl S. discusses the danger of confusion inherent in naming the slants based on how they look from the front. Cheryl is 100% correct, and if I could think of a better way to name these, I totally would. The photo that Rachmouse asked for perfectly illustrates Cheryl's point: As you can see the decrease which WILL be LEFT facing from the front is part of a line of RIGHT SLANTING decreases from the back. Similarly, the decrease which WILL be RIGHT facing from the front is part of a line of LEFT SLANTING decreases from the back. So, be warned -- look at the front frequently to be sure that your purled decreases slant the way you want them to, and don't put too much stock in what these purled decreases are called. And now, here's the photo Rachmouse requested:

You have been reading TECHknitting blog on "Purled decreases: p2tog, SSP, p2tbl, p2togtbl"


quinn said...

The left-leaner is something I would have driven myself nutso trying to figure out, if not for your clear description AND diagrams! Thanks so much!!

mon bouton said...

brilliant work !
as usual..
I'm really glad to see you back more often :)

amelia said...

good gourd, i love this blog so much. <3

Cheryl S. said...

I love your site, and have gotten some great information.

This post is great in explaining the difference between the purl decreases, and how they relate to both sides of the fabric.

However, while I don't disagree with anything you said, I do have a minor issue with the whole concept.

I'm probably in the minority on this, but I personally have a real problem with calling purl decreases left-leaning and right-leaning based on how they are seen from the "other" (supposedly right side) of the fabric.

If I'm doing the decreases on a sleeve cap, for instance, I know visually whether I want the stitch to slant to the left or the right (away from the body of the fabric or towards it). If I'm at the right edge of the fabric and I want the stitch to slant away from the fabric towards the selvedge, I'm going to think of that as a "right-leaning" decrease, regardless of whether I'm working on the RS or WS, since it will be slanting to the right edge of the fabric as I'm looking at it. It's terribly confusing to me to have to stop and think of what it would look like from the OTHER side.

And as it happens, I recently had a project in which I was doing decreases along the neckline of a garment done in rib. Some of the purl stitches WERE the right side, and it did have p2tog and p2tbl decreases. I agree with you that they really didn't look any different from the right (purl) side. But nonetheless, calling them right-leaning and left-leaning as seen from the front side made no sense at all. And if all I did were p2togs, the neckline decreases would have looked strange from the wrong side, and it would have bugged me.

Even worse, I tried to chart the pattern in Knit Visualizer to make it easier for me to follow the pattern. But it also considers a p2tog as a right-leaning decrease even when worked from the right side, so either the chart was wrong visually but had the right instructions, or the instructions were wrong but the chart was visually correct.

I just think that calling purl decreases left- or right-leaning is going to be confusing unless that description comes with an explanation as clear as yours. But unfortunately, in most cases they will just be called one or the other, without indicating whether that's as seen from the purl side or knit side.

But anyway, thanks for another good post.

--TECHknitter said...

Hi Cheryl. You're completely correct--the whole "which way does it slant" thing is a mess for the exact reasons you state. In fact, I struggled with this terminology for a long time, which is why so basic a post has only come out after such a long time.

However, what finally convinced me to think about the direction of lean AS SEEN FROM THE FRONT (or stated otherwise, from the "knit side") is the fact that, as seen from the back (or from a column of purl on the front) the direction of lean really doesn't show, not even in a paired decrease situation (or at at least I should say, I personally can't see any difference).

It's a mess, yes, but this is my best stab at straightening it all out!

Thanks for writing--TK

kmkat said...

Oh, thank you (again)! I have not knit a pattern that called for these, but sometimes my mods to a pattern might require decreasing on a WS row. Now I know what to do!

Purple Butterfly said...

Thanks for another thorough, detailed, EASY to understand tutorial.

thistledown musings said...

Great! I can never remember these things (I blame it on my being left handed and never being able to give directions as to me my left hand is dominant while most other folk's right hand is dominant, so I call left "right" and right "left"). See why I am confused?

C said...

Thanks for another great post! This is one of those things that I had to figure out the hard way, with a lot of tears and frogging.

I also like to think of it as "left-leaning" in relation to the knit (front) side. I realized when I was doing a cable pattern the other day that I tend to think of things in terms of the front of the garment by default (i.e. a knit stitch on the wrong side is just the back of a purl stitch and vice versa), so the way you explain it makes perfect sense to me. I guess people just have different ways of thinking and visualizing!

P.S. Speaking of cabling, do you have any future plans to do a post about cables?

Sally said...

Thanks for these clear directions! I do have a question, though - in the ssp/p2tbl, why do you transfer the loops back to the left needle before purling? is there a way to get the same result by inserting the left needle into the loops stored on the right needle? (similar to the ssk)

--TECHknitter said...

Hi C: One day, I will tackle cables, but not just yet. They are a huge subject which'll take quite a few posts, and there's lots of other stuff to get out of the way first. One day, though...

Hi Sally: I don't think what you're talking about is do-able. In ssk as in spp, the slipping step re-orients the stitches to lay left arm forward. But, there's an additional step in ssp.

In ssk, the stitches aren't knit out of order. In other words, they are worked off the left needle in the same order in which they lie--the right needle inserts first into the first stitch at the tip of the left needle, and then into the second stitch in from the tip of the left needle.

By contrast, the stitches in ssp must be worked off the left needle in reverse order--second stitch in from the L needle tip is inserted first, then comes the stitch closest to the L needle tip. To accomplish the re-arrangement, it's necessary to re-position the R needle after the slipping step, and that's why there's one extra step in ssp compared to ssk.

But hey, I've been wrong before and will be again! If you find a way to do ssp in one smooth swoop let me know right away because maybe I'm overlooking something!?!

Thanks to C and Sally and all the commenters for writing.


rachmouse said...

Great post as usual...

Can you also post a picture of what those decreases look like on the purl side? Just for reference and curiosity's sake... :-)

--TECHknitter said...

Hi Rachmouse: Done!


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bibliotecaria said...

These aren't the only two purl decreases, right? Just the most common ones?

And -- is there a way to do a decrease, knit or purl, that does not show a direction?

Evelyn said...

In illustration 2, it looks like the working yarn is behind the needle, but in illustration 3, it is coming from the front. Would we need to move the yarn to the front for a purl before we slip the stitches, or is this illustration accurate? (Or am I missing something?)

Evelyn said...

Ok, I think I was wrong. After you slip the stitches, you also slip them back again, so you can bring the yarn forward after all the slipping is done. So the illustrations are accurate (no surprise there!) and the confusion is all mine.

ifdefelseif said...

I figured out the left-leaning purl on my own (having noticed the usual instructions leave the stitch twisted), but always wondered if there was a more efficient way to do it. Seeing your instructions is comforting--if you do it the same way, then I'm satisfied that I haven't missed some clever trick. :-)

CricketB said...

Another great post.

I agree with "as seen from the front" terminology. It emphasizes the look of the final product. I learned to "knit back backwards", not to avoid turning at the end of rows, but so I could see the result from the front.

--TECHknitter said...

Hi Bibliotecaria: The decreases shown here are single decreases--that is--one stitch is lost with each decrease performed. All other single purl decreases are variations on the ones shown here, and all single decreases lean in one direction or another. Not all purl decreases are single decreases, however. It is possible to make 3 stitches into 1 stitch (a double decrease) and these sorts of decreases can be created non-leaning.

Hi Evelyn--THANKS for your comment. I overlooked writing into the instructions that the running yarn should be brought forward between steps 2 and 3. Thanks to your eagle-eyed catch, that instruction has now been inserted. Thanks very much, again, for writing.

Thanks also to all who have commented. Purl decreases are a nomenclature mess, so it's great to get feedback.

The Bukharan said...

jeez, when are you going to get a book contract?!?

Jeny Staiman said...
This comment has been removed by the author.
Jeny Staiman said...
This comment has been removed by the author.
Jeny Staiman said...

Let's try that again...

Hi Sally and TK, this is in response to the question of whether or not there is a way to get the same result by inserting the left needle into the loops stored on the right needle. There is! I've already chatted with TK about this offline and she agrees that my variation is legit, so I am sharing it here.

I don't have illustrations so this description will have to be a bit detailed... Here's how you do it:

Step 1 - same as TK.
Step 2 - (do not return the two sts to the L needle) From L-R, insert the L needle through the two sts such that it is in front of the R needle from the knitter's perspective.
Step 3 - Bring the working yarn behind, then around and in front of the L needle and use your L needle to draw this loop through the two sts. This is awkward, but persevere. :) You have now purled the 2 sts together, but the new st is on your L needle.
Step 4 - Slip the new st from L to R needle, changing the orientation as you slip; insert R needle through back loop, from back to front, then slip off. Note that If you were to slip knitwise, you'd put an extra twist into the stitch.

This is a different way of achieving the exact same result as TK's ssp. It's just a matter of preference.

It's theoretically possible to wrap your yarn around your L needle such that you can skip that last re-orientation, but I still find it easier to do this way. However, there is no way (as far as I can tell) to avoid re-orienting the two sts you are going to purl together, which by nature means you have to move them twice -- first L-R, then back R-L. TK passes them back R-L *before* they are purled together, and works the decrease with the R needle; this means the resulting decrease st is already in place to continue purling. I work the st with the L needle, which means the resulting decrease needs to be moved back to the R needle in order to continue purling -- essentially passing the 2 sts back from R-L *after* they are worked.

Hope this helps!

--TECHknitter said...

Thanks, Jeny, for your detailed description!

Carla said...

This is a great tutorial, and the detailed/easy to read drawings are the best I've seen. I'm so impressed.
Thanks so much for the great instructions. I'm a beginning knitter, having only knit several hats and scarves. These tutorials open up a whole new world of knitting.
I'm printing out your posts in color and putting them into a notebook for future reference.

kristen said...

Hi - excellent post. Thorough and thoughtful as usual!

I thought you might enjoy Barbara Walker's recommended shortcut for working p2togTBL - she suggested that you (1) purl the first stitch normally, (2) return the stitch just knitted to the right hand needle, then (3) pass the slipped stitch over it.

The resulting stitch is neat and smooth on the front of the work and looks just fine on the back.

While this method sounds like a PITA, I find that it is far less awkward than trying to get the right-hand needle through those back loops left-to-right as for an SSP. I just can't ever seem to do that without cussing a whole bunch!

Thanks again for the awesome post.

kristen said...

...whoops, in my last comment I meant pass the *next* stitch to the left over the stitch just knitted.

Jody said...

I have been doing p2togtbl with no problem (pointy tips help!), but I've never done the ss part first to reorient the stitches. I have no knitting in front of me, but I assume it's so that the finished decrease has no twist in it? I've done it on lace where I didn't really notice it. I will have to make a mental note to try it this way on my next project. I wonder if it makes the third step easier...

Anonymous said...

I am quite a seasoned knitter and I would like to say these diagrams are BAR FAR the best I have seen. Your combination of written directions and diagrams are even better than some videos! Thank you so much for taking the time to do this for us!

AdaKnits said...

WOw - this is amazing. Most beneficial to me was the explanation of the ssp. As others have said, the explanation and diagrams here are absolutely outstanding! Thank you for this amazing contribution to knitting!

Anonymous said...

Thank You! I get it now!

laura said...

thanks! i never had to make a left leaning decrease from the purl side before and no matter what i made up that seemed right would work. so glad i searched it and you popped right up! your blog rocks!

i'll be back for sure!

Anonymous said...

Thank you! I am trying to do decreasing in double knitting so assuming the "stockinette" side is the "knit side" made no sense at all. Likewise, the right and left slant were not making much sense due to the mirror nature of the work. Now I get what I need to do, if not the way things are named.

Robin R said...

So very sorry. Just got out my yarn and needles, and this method of yours is THE BEST. It also pairs wonderfully with the p2tog decreases at the beginning of the purl row. So, would you please just ignore my last comments? I would be obliged, as I am to you for all the incredible methods you outline for us so clearly. I don't know how you do it, but I'm glad you do!!!!

Anonymous said...

Thank you for writing these pages. They are invaluable for my knitting.

Unknown said...

Thanks so much. I have been knitting as a true lefty for many years.

I am guessing all I need to do to make this work is do the opposite.


PS I have tried many times to convert to rightie,

Anonymous said...

Thanks so much for this clear and simple explanation. As an apprentice knitter I am making my first cabled sweater and my armhole decreases on the back were looking a bit like a dogs body. I am now armed to do the front much better!

craftycrusader said...

Very useful post to refer to, thanks!

Anonymous said...

Very clear diagrams,brilliant!

Wonkey Donkey said...

June Hemmons Hiatt has an alternative method similar to the Barbara Walker one described above -- purl the first stitch, then slip the second knitwise. Put them both back on the left needle, and pull the second stitch (the re-orientated one) over the first stitch (which had been purled). Then put the final result on the right needle, tightening it before continuing. She calls it Purl Slip Pullover.

Anonymous said...

Thanks for explaining. To make it easier to remember which decrease to use where, consider this: from the 'knit' side of the fabric, p2tog looks like k2tog; and ssptbl looks like ssk. I've tried the 'Purl slip pullover'; alone it looks fine, but if it's paired (say, with a p2tog) they do not match very well.