Double knitting: the What and the How History(ish), Theory, How-to demos

"Double Knitting" has two meanings. It can refer to a weight of yarn, or it can refer to reversible knit fabric. Going forward, I'll call the yarn "DK weight yarn," and the fabric "double knitting." This series is about the reversible fabric, shown here on a sock in progress. 

SERIES PREVIEW

I've said that double knitting is a reversible knit fabric. Usually, but not always, both fabric faces are knit at the same time. However, it is possible to create double knitting in unconventional ways, out of two entirely separate pieces of fabric, or out of a striped fabric, or by rows knit independent of one another, and each of these tricks will be shown as part of this series.

Usually, but not always, the reversible fabric is knit from one needle to another, a total of two needle tips. However, it is possible to work in an unconventional way and create double knitting on four needle tips, operated at the same time. I have prepared two videos about this trick, also coming up in a future installment.

Usually, but not always, the front and back faces of the reversible fabric are mirror images. However, it is possible to create double knitting in unconventional ways, so the two sides have entirely different designs. Words picked out in contrast color stitches, for example, can be made to read correctly on both sides by using this trick. 

It is also possible to work double knitting so the front and back have different textures, such as one side cabled, and the other smooth. Texture words (purl on stockinette background) can also be knit, reading correctly from both sides. 

 Color work in double knitting is usually restricted to two colors, those being the ones which switch between front and back fabric faces. But, by unconventional methods, it is possible to add further contrast colors on one or both sides. Again, each of these tricks will be covered in future installments.

Double knitting makes s a two-layer fabric. Usually, the two layers lie back-to back, making a flat fabric. However, it is possible to stuff the fabric, either in squares like a quilt, or in columns, like a puffer vest, or even in 3-D circles like balloons: yet another future installment.

In double knitting, the top and bottom edges, as well as the side edges, are often troublesome. Some basic info on casting on, casting off, and working side edges has already been published. There will be more to come. 

Reading charts for double knitting can be complicated where the design is not symmetrical, either bilaterally (not same on left and right sides) or from face to face. This, too, will be addressed. 

And of course, it is easily possible to make mistakes, but it is also possible to correct them: yet another future installment.

What a lot of double knitting coming up! But today's post starts at the very beginning, with an imaginary history and a look at the theory. The post wraps up with some demos to follow along with if you wish. Classic alternating-stitch double knitting is shown, in "one pass" and "two-pass" variations. 

My IMAGINARY HISTORY of double knitting

In Leo Tolstoy’s famous book, War and Peace, (published 1869) Anna Makarovna is knitting socks with a big secret. Here is the big reveal:

…[B]reathless cr[ies] of children’s voices filled the room. “Two, two” they shouted.

This meant two stockings, which by a secret process known only to herself Anna Makarovna used to knit at the same time on the same needles, and which, when they were ready, she always triumphantly drew, one out of the other, in the children’s presence.

As described by Tolstoy, the fictional Anna is knitting socks, one inside the other. By using two separate balls of yarn to work alternate stitches, she actually creates two separate fabrics at the same time, on the same needles. If you want to try this form of extreme sock knitting yourself, there's more info at the end of this post.

But my imaginary history of double knitting goes in a different direction.

In my version, Anna gathers the children around and pulls, but … the socks do not come apart. They are stuck together by a few stitches here and there. Distracted in her knitting, Anna has accidently confused the yarns. Perhaps she used the yarn from the outside sock to work a stitch on the inside sock, or perhaps the inside yarn to work an outside stitch. So now, the two socks are stuck together. Oops! There is a way to fix a goof like this, but it doesn’t come until several installments later in this series, too late for Anna Makarovna. So, oh well! Anna fastens the tops of the layers together, then pulls this first, double thick sock on one foot and casts on again.

Determined to do better this time, Anna casts on two different colors of yarn: black outside, white inside. This will make it easier to see which yarn goes where. Yet, once again, distraction strikes. Anna has absentmindedly used the black yarn to work a few stitches along the hidden white inside sock. Not noticed at the time, these stitches become evident when the stuck-together socks are turned inside out. A second oops, a second double-thick sock. She again fastens the tops together, then pulls this second mistake onto her other foot.

But hmmm … what if…

Looking at the second sock, Anna thinks the contrasting color stitches look pretty--a pleasing contrast. Plus, the double thick socks on her feet make a cozy pair. So what if, on the third attempt, she begins by fastening the layers together, then purposely uses the black to work a few patterns on the white inside, while using the white to work a few patterns on the black outside? It wouldn't be two socks, like she was originally trying for. Instead, it would be something new:  a single reversible double-thick sock with mirror image color patterns.

...It would be a reversible sock with mirror image color patterns...

In my imaginary history of double knitting, Anna’s third sock is a triumph: the first purpose-made double knit garment ever.

Is this the way it happened? I'm not enough of a knitting scholar to know in which order these tricks emerged. But my invented history isn't completely far-fetched. 

By the 1860's, Tolstoy had seen someone knitting this way: the details are too intricate to make up. He put the knitting in the hands of Anna, a long-time caretaker in a traditional and aristocratic Russian household, a character likely to be old fashioned. Such details point to an older origin. And, in my experience, it sure is easy to confuse the front fabric with the back when knitting Anna's sock-in-a-sock trick. 

So, it's no great leap to imagine a long-ago knitter with two stuck-together socks taking the next logical step: accidental-done-on-purpose color patterns. A happy accident which went from mistakes in socks to give rise to reversible double knitting

Just to be clear: I absolutely made up this whole scenario! And Anna wasn't even a real person anyhow, just a character in a long-ago novel. But, you know, double knitting reversible fabrics could have been invented this way. 

Visualizing two separate fabrics knit at the same time on the same needles

What the heck was the fictional Anna actually doing? How is it possible to knit two different fabrics at the same time on the same needles?

We'll see more of Anna's sock in the future. But for now,  small samples knit back and forth make it easier to recreate Anna's journey, from independent fabrics, through to mistakes, then on to reversible color patterns in double knitting. 

Two yarns, two fabrics--Anna's plan

--Below, two 8-stitch scraps. Above the cast on, the green is worked one row higher than the white. Because of green's extra row, when I go to hold the fabrics back to back (purl sides together) the running yarn is on the right side of each fabric (red arrows).
--If you are mirror-image knitting, sometimes called "left handed knitting," switch right for left.

--Step 2: I hold the green behind the white, with both needles in my left hand. I slip each stitch, alternately, onto a third needle held in my right hand. 
--Step 3: all the stitches are on board the single needle.

--In step 4, I take a needle in my right hand and switch BOTH running yarns to the front. I purl a green stitch using the green running yarn.
--In step 5, I now switch both yarns to the back. Dropping the green, I now knit the next stitch in line, white, with the white running yarn.  
--I repeat steps 4 and 5 down the row, alternately purling the green stitches with green, while knitting the white stitches with white. Although I am only using one yarn at a time, both yarns travel back and forth as I purl green with green, knit white with white. In this way, the yarns do not cross. 

4: purl the green stitches with green yarn. 5: knit the white stitches with white yarn.

Photo 6 shows my progress partway down the row. Four stitches of each color have been worked, a total of eight stitches. Now it's time for a true confession: there's no reason to be dropping and picking up the colors. It's possible to hold them both at the same time, just "picking" at the color you need with the working (right) needle. With respect to yarn handing, this is the same trick as for working stranded knitting holding two colors at the same time. The important thing is that the yarns do not cross,  and that each stitch is made with a yarn which runs directly back to the skein for that color. 

After a few more rows, I see that my work can be flipped open like a book, with the needle as the hinge. (7). If I pull the needle out all the way, two separate fabrics fall off the needle (8). Shown are the purl (reverse stockinette) sides, but, of course, the other side of each fabric is a little knit scrap of stockinette. 

This is how Anna planned her sock-in-a-sock trick: the inside sock purled with yarn from one skein, the outside sock knit with yarn from a second skein. Her aim was, that at no time would the two yarns cross. In this way, the fabrics would remain separated, two socks could be knit at the same time on one set of needles, and one sock could be drawn out of the other at the end. Clever Anna! (Again, more about sock-in-a-sock at the end of this post.)

Two yarns, one stuck-together fabric--Anna's mistake

In my imaginary history, Anna gathered the children around her, but the socks did not pull out of one another. This is because, distracted, Anna mistakenly used the front yarn to purl a back stitch, or the back yarn to knit a front stitch (or both!) 

To reproduce Anna's mistake, I work in two colors, white and brown this time, so the mistake is obvious. I again start with 8-stitch scraps. I hold the brown behind the white. Per step 1, above, the fabrics are held back-to-back, purl sides touching. Per step 2, above, onto the third needle, I again slip alternate stitches--brown, white, brown, and so on. This photo shows what I have on my needles. after the final slipping.

How it started

Using the brown yarn I purl the first brown back stitch, then using the white yarn, knit the second front white stitch, each color with its own yarn. I repeat this sequence twice more, working down this row until 3 brown stitches have been purled, and three white stitches have been knit. I have been switching my yarns back and forth with each stitch, so there is no tangling. So far, so good. The pattern on my needle is as expected, as shown by this schematic

PATTERN AS EXPECTED, partway down the row

Recollect that the work proceeds from <---- right to left.

But now, the mistake! Instead of purling the next back stitch in brown, I've purled it in white! I compound the mistake by knitting the next front stitch in brown instead of knitting it in white! And then, I make the same two mistakes again! In schematic, the pattern on my needles is now as follows

MISTAKE STARTS AT GRAY LINE, AND APPEARS IN RED BORDERED AREA

Again, proceeding from <---- right to left. 

If I was trying to make two separate fabrics on the same needle, these center 4 stitches in the red bordered cells have each been worked in opposite colors to how they should have been. 

I work the following remaining stitches in correct pattern, but the mistake in the middle remains. This is what the mistake looks like in schematic: the mistake is bordered in red, between the gray projecting lines. 

MISTAKE IS BETWEEN GRAY LINES, IN RED BORDERED AREA

This is how the mistake looks in real life, again bordered in red. I have accidentally purled two back stitches in white, and knit two front stitches in brown. The center four stitches are a "switching mistake," meaning I have switched front yarn for back, and back yarn for front.

How it's going--switching mistake

It's easy to see that this kind of mistake could pass unnoticed, especially if I, like Anna, had children buzzing around. And of course, in my imaginary history, Anna's first mistake would have been made when she was knitting a pair of normal (same color) socks. I worked my sample in two colors to highlight the mistake, but if both fabrics were in the same color, switching mistakes would be very much harder to see. 

 I work a few more rows without further mistake. However, the two odd stitches on each fabric face are obvious, and when I try to open the fabrics like a book to separate them, I cannot. The two fabrics are stuck together in the middle where white and brown changed places. This is why, in my story, Anna could not pull one sock out of the other--her switching mistake fastened the two layers together. 

How it ended up: stuck together by mistake

One double-sided fabric with color designs--Anna invents "classic" double knitting

In two colors, you can see that switching mistakes easily give rise to the idea of making purposeful designs. So, in my imaginary history, Anna now sets off to make designs on a double-thick reversible sock. She charts an easy design--a diamond. five rows high, five stitches wide, centered in a repeat of 13 rows and 11 stitches. 

Anna's previous double-thick socks--mistakenly bound together by switching errors--had to be fastened together at the top after the fact.  But in this final stage of her journey, she thinks ahead, and begins the work by fastening the two layers together beforehand. 

Diamond knit flat

This sample--my recreation of Anna's final step--also starts as two fabrics fastened together. Anna knit in the round, but my recreation is knit flat, back and forth, to better show the action.  To make the diamond charted above, I have cast on 11 stitches of each color, making a joined fabric. Instructions at this link show how to make this kind of purl-looking cast on and work the first few rows for a double knitting project. 

Fabrics cast on and joined

So far, this fabric is only joined at the cast on, but I am now ready to begin double knitting from the diamond chart above. I therefore rearrange the stitches on my needle so they alternate. Alternating stitches are the classic set up for double knitting, just as they are for individual fabrics. 

Alternating stitch set-up for classic double knitting

If you look closely, you see I am slipping the first stitch (edge stitch) of each color, as described here. 

Geek Note: In fact, if you look closely at all the little scraps in this entire post, I actually always slip my first stitch. However, to keep things simpler, I don't always make a point of it in the directions.

First row

On the first row of the chart, I begin with the white fabric face towards me. I work the first five stitches each side, alternately, each stitch in its own color. On the center stitch, marked in red, I switch, knitting a blue stitch on the white fabric, and a purling a white stitch on the blue fabric.  The remaining five stitches of this row on each fabric face are then each worked in their own color.

 Below, the work at the end of the first row. If you think this looks similar to the out-of-order stitches in the "mistake" portion, you're right. Here, one stitch on each fabric face (between the red arrow) has disarranged the alternating stitch order, while the mistake featured two stitches, but otherwise, this is the same maneuver.  In this case, the maneuver is on purpose, intended to create the contrast color stitch at the bottom point of the diamond. 

First row: one set of stitches in alternative placement

Second row

Because I am working flat, in order to work the second row, I must turn the fabric. Now, the blue face is towards me, the white, away.  Because the design is bilaterally symmetrical (same left and right), and because the design is centered, the stitches switch in the same location, regardless which fabric face is towards me. Therefore, the chart remains a good guide. (This will not always be true--an asymmetric design cannot be read both ways if working flat. There will be more about chart reading coming up.)

The chart shows that I must switch to contrast color for the center 3 stitches.  The background stitches on ether side of these center stitches are worked, each with its own yarn in its own color, alternating stitches, front and back from the two different yarns. At the end of the work, this is what I see. Again, the diamond pattern stitches are between the red arrows. 

 

Second row: three sets of stitches in alternative placement

Third row

On row 3 of my chart, the white fabric face is towards me, the blue, away. In the photo below, you can see the diamond building upwards by contrast color stitches on the fabric, topped by the disturbance in the alternating pattern of stitches on the needle: what started as a uniform field of alternating stitches has now been interrupted by the upwards rising triangle which makes up the bottom part of the diamond. The center five stitches--the widest row of the diamond--are between the red arrows. 

Third row: five sets of stitches in alternative placement

Diamond completed

I continue in this way, following the chart for the remaining two rows of the diamond. I end by working several rows in each color to match the bottom, working alternating stitches in pattern such that all the white stitches are on the white fabric face, and all the blue on the blue. At the end, the stitches are again separated onto two needles, as they were at the beginning: this is the set up for casting off in purl, according to these directions. 

Diamond completed, layers separated to work purl bind off

Result below: little reversible diamond-centered scraps. 

Diamond in the round

Earlier, there was a short video of a black and white sock top--and this is more like what Anna might actually have created if she'd wanted a double-knit, double-thick reversible sock. Worked in the round, it features the same diamond pattern shown on my sample scrap. It, too, is fastened together at the top by the purl-looking cast on here. It is worked the same as the blue and white diamond above with one exception. Because the work is in the round, the same side (black in the video) is always knit along the outside, while the inner is always purled (white).  The next installment will have further info on this black-and-white sock.

Another diamond, another method -- "two-pass" classic double knitting

In my imaginary history-ish, I've made Tolstoy's Anna the inventor of double knitting. But she might actually have knitted her original sock-in-a-sock in a slightly different way than any I have shown so far. This is because there is a different path to the same end. It is called "two-pass double knitting." Two-pass double knitting is especially useful for the kind of plain rows and rounds Anna would have been knitting when Tolstoy invented her, but can be used for colorful shapes and patterns as well.

Just to be clear: the kind of double knitting we have been looking at so far is worked sequentially on alternating stitches, worked in one pass. EACH pass through a row or round leaves that row or round complete. In fact, a technical name for this kind of classic double knitting is "alternate stitch, one-pass double knitting."  By contrast, in two-pass double knitting, it takes TWO passes to complete a row or round. 

To explain: Recall that on the white and green sample, above (first sample, separate fabrics) the knit stitches of the front fabric were worked with the yarn of that color, while the stitches of the back fabric are purled with the yarn of the back color. These stitches were worked as they present themselves on the needle: alternately. The yarn switched in my hand from stitch to stitch.

However, a different path to the same end allows me to complete the entire row or round without constantly alternating the yarn.  Below, my gold and white stitches were cast on as shown here, and are now arranged alternately on a double pointed needle or a circular needle. In this view, the fabric face towards me is gold, the one behind is white. There are three stockinette rows worked--I am including the loops on the needles as a row for this count. Both running yarns are to the right, waiting to be worked (red arrows) 

This diagram shows the same fabric. The diagram shows BOTH fabric faces at once: the gold front fabric is shown to the left, and the back white fabric to the right. The diagonal stripes  ╲  show that white layer is purled. As in the photo, on this diagram there are three rows worked: three gold on front, three white on back. The little tails sticking up show where the running yarn attaches. On both fabrics, as on the real life sample, the running yarns protrude to the upper right.

I begin by working a gold stitch. Then I bring the gold yarn to the FRONT and SLIP the intervening white stitch. 

IMPORTANT: the white stitch is slipped "open," meaning, not twisted in any way, just merely transferred from one needle to the other, maintaining the "right arm forward" orientation of the slipped stitch. 

I then bring the yarn to the back and knit the next gold stitch, then again bring the gold yarn to the FRONT and SLIP the next intervening white stitch. The below photo shows the third white stitch being slipped, with the gold yarn held in front. Again, the red arrows point to the running yarn. As you see, the white running yarn has not moved from the right side of the fabric. It is only the gold yarn which is being worked.

Slipping the white while holding the gold yarn in front. Red arrows point to running yarns.

I continue knitting gold and slipping white all the way down the row, always bringing the gold to the front when slipping a white. 

Again, what I'm doing in this "first pass" is working the FRONT (gold) fabric only. The back (white) stitches are not worked, but are only slipped. By this means, the front fabric now has FOUR rows and the gold running yarn is at the left side of the fabric. In this photo, you can't see the back of the fabric, but you can surmise that there are still only three rows of the white, because the white running yarn has remained at the right side of the fabric (right red arrow). 

The diagram is as follows: as in real life, the gold running yarn is to upper left, the white to upper right. 

At the end of the first pass, I slide the work back to the other point of the DPN. I now work the "second pass." I begin working a white stitch. Then I bring the white yarn to the BACK and SLIP the intervening gold stitch. Again, the stitch is slipped "open." I then bring the yarn to the front again to purl the next white stitch, then again bring the white yarn to the BACK and SLIP the next intervening gold stitch. In this photo, I have worked two white stitches, and am slipping the second gold stitch with the white yarn (red arrow) held to the back.

Slipping the gold while holding the white running yarn (red arrow) in back

 I continue purling white and slipping gold all the way down the row, always bringing the white to the back when slipping a gold. 

The front of the fabric has changed very little, but you can surmise that the white back row has been worked because the white running yarn has now joined the gold running yarn on the left side of the fabric (red arrows). 

The diagram is more revealing because it shows both front and back. As you see, there are now four rows on each fabric, and as in real life, both running yarns are to the left side of the fabric.

Do you wonder why I must bring the yarn forward when knitting + slipping, or back when purling + slipping? By so doing, I am actually traveling the yarn "up the middle," between the two fabric layers. If I fail to bring the yarn forward (knitting) or backward (purling) I will "lasso" a stitch with a contrast color bar, per below photo at red arrow.

Lassoing a stitch isn't a dreadful mistake. If I catch it while working the next pass, I can simply wiggle the gold stitch out from under the white (contrast color) bar before working the gold stitch. This returns the bar to run between the fabrics where it belongs. It gets a little more complicated if I only notice the bar a few passes later. To correct, I'd then have to ladder down some stitches, wiggle out the lassoed stitch and then hook up the ladder again. Checking for lassoed stitches is why it is a good idea to inspect the work, both front and back, before working the next pass.  (There will be more about correcting errors in an upcoming installment.)

 Working flat, it is my habit to work first the knit side, then the purl side. If working circularly, I knit an outside round, followed by purling an inside round. The exact order does not matter much, but it is a good idea to be consistent, and a VERY good rule is to ALWAYS work both passes before quitting for the night. Half-rows are less likely to get out of synch if you remain consistent in work order and do not put down the work until both halves of the top row have been worked. 

So far, I have worked one row in two passes: the front pass in gold, the back pass in white. This has added a same-color row to each side. You can see how this would work for making two separate fabrics at the same time on one needle, such as how Anna might have been knitting her socks when Tolstoy invented her.

Overview

With shapes and contrast color knitting, two-pass double knitting gets a little more complicated. To demo, here is the overview schematic of the diamond pattern, the same design previously worked above in blue and white as a one-pass project, and on the black and white sock in one-pass circular. 

This time, it is to be worked in gold and white as a two-pass project. The four white-and-gold rows previously worked in the above photos and diagrams will now serve as the four rows below the diamond.

As shown in this partial chart,  first row of the diamond requires that the middle stitch be worked in a contrasting color--this is the bottom point of the diamond.

 Because I am working flat, I must flip the fabric. I am now working with the white fabric face towards me. Because I always work the knit side first, I set off knitting + slipping in white. On the sixth stitch (bottom point of the diamond) I switch up. Using white, I PURL into sixth GOLD stitch, then SLIP the sixth white (front) stitch, per the overview. Purling into the gold stitch yields the white stitch at the bottom tip of the diamond as it will appear on the back fabric--a white diamond on a gold background. Slipping the sixth white stitch on the front sets that stitch up to be knit in gold on the second pass-though. I finish the row by knitting the whites and slipping the golds. 

Here is the fabric after the first pass through--the white running yarn is to left, the gold to right (red arrows). There appear to be three white stitches in a row between the green arrows, and the middle one is the purled center stitch on the back fabric--if you squint, you can see the gold collar around its little neck from the (gold) stitch in the row below.

First pass, row 5

Here is the chart which better shows what actually happened. Just as my fabric flipped, so my chart also flips. White now represented on the left (front) side, gold represented on the right (back) side. Again, the diagonal stripes   ╲  show purled fabric. The white purled stitch in position 6. The fifth row of white has been worked, but not straight across one layer, as previously. Instead, the stitches of row 5 appear partially on the front and partially on the back. The top of the fabric does not look uneven in the photo because the needle is constraining all the loops to lay in a straight row, but the diagram shows that, if the needle were not in the way, the fabric would be uneven along the top after this half-row.

On the second pass, using gold, I purl the gold and slip the white, EXCEPT that I SLIP the already worked white center stitch in back, and KNIT the previously slipped center front stitch in front. In this way, the rest of row 5 is filled in on the back, and the missing center stitch is filled in on the front with the required contrasting color. 

After the second pass, the fabric looks like this, and the chart like this. On the photo, the running yarns are at left (red arrows) showing the row has been completed, and the stubs on the chart agree. 

Second pass, row 5. Compare this photo to the blue-and-white one-pass project after the bottom point of the diamond has been worked: they are the same. 

The rest of the diamond is worked the same way: on the first pass, the front color is knitted on the front, slipped over the intervening stitches EXCEPT where it is purled onto the back and slipped on the front, as indicated by the chart. Similarly, the back color is purled on the back and slipped over the intervening stitches EXCEPT where it is knit onto the front and slipped on the back, as indicated by the chart.  Above the diamond, several rows are then worked in background color, to match the rows under the diamond. The end result of working the diamond in two-pass knitting is identical in every way to the previous diamonds (blue and white, and black and white around the sock top) which were worked with the one-pass method. 

In many ways, the two-pass method resembles a technique called "multiple pass color knitting," which is a trick for working more than two colors when doing stranded color work (not reversible). If inclined to go down that particular rabbit hole, here is the link to that technique.

Two pass vs. one-pass

Where there is no color switching between fabric faces (sock-in-a-sock for example) two-pass is probably quicker than one-pass: if I absolutely had to knit sock-in-a-sock in a single color per sock, I'd use the two-pass method. (More about sock-in-sock below.)

For reversible patterned fabrics, I normally prefer one-pass, because figuring out where I am in the half-rows makes two-pass slower for me. However, if you have the kind of mind which can keep track of complex partial rows, you may find two-pass quicker, even where there is a lot of switching. This is because there is less yarn dropping and starting again. I have observed many fine knitters who do prefer two-pass for all double knitting.

If just starting out, consider trying both one- and two-pass to see which you prefer. The little diamond shapes demoed above would make a dandy intro to double knitting, and could be tried both ways.

However! These are not the only two alternatives. As this series unfolds, there will be several other methods. So maybe don't settle on a final choice just yet.

Looking backward and forward

In this post, the fictional Anna has journeyed from independent fabrics to "classic" (alternate stitch) double knitting via the one-pass method, as well as the two-pass. The next installment backtracks a little, to feature classic double knitting combined with independent layers of fabric--we will see more of Anna's black and white sock, as well. See you then.

--TK

Questions? Feedback? Contact me at 

Blue Sky  @techknitter.bsky.social or  talk to me about this post on Ravelry TECHknitter forum

More about sock-in-sock:

--To be clear, sock-in-a-sock IS a double knitting technique because you are creating two fabrics on one set of needles. However, unlike most other double knitting, sock-in-a-sock doesn't make reversible fabric: each sock really is an independent item and at the end, you really do draw one out of the other, just as Tolstoy had Anna do. It's only if you make mistakes that the two socks stick together. If you DO want reversible designs, then you're not really knitting sock-in-a-sock, but you're double knitting ONE reversible sock--just like the black and white sock cuff in the intro photo as well as the video above. There will be more about that reversible sock in the very next installment.

-- Here's a tutorial for sock-in-a-sock. If that link fails, here’s an archival link for the same tutorial on the wayback machine. Archival links take a long time to load, you may have to scroll down a blank page to where the link starts, and it may require several re-loads to get the pictures. But, archival links are as "forever" as the web gets, so there's that. 

--It is standard to hold the two fabrics back-to-back for reversible double knitting. However, for sock-in-a-sock, you could hold the fabrics back-to-front, meaning, knitting both layers and running the yarn BEHIND each fabric as you made it--the front yarn running behind the front fabric (which actually means it runs in-between the two fabric layers) and the back yarn running behind the back fabric. As long as the yarns don't cross, this method also makes two separate fabrics. In fact, the sock-in-a-sock tutorial linked above does it that way. However, I, personally find it a lot easier to mistake back and front fabric when working both the same. Knitting one and purling the other works better for me, with both yarns running between the fabrics. (And since this is my story to tell, I had Anna do it my way, too, in my little fake history at the start of this post.) 

--If serious about trying sock-in-a-sock, perhaps consider making the inside and outside socks different colors, and then working the same two colors in the same order for ANOTHER sock-in-a-sock. This would give you two matching pairs in the end. With two different colors for each project, there's less likelihood of making switching mistakes. Further, the inside and outside sock aren't ever really the same circumference (size around) but by making two sets of two socks in the same order and on the same needles, each sock would at least match its partner, circumference-wise.

-- Knitting one sock inside another makes for looser fabric on both socks, so knit more tightly on smaller needles to get the gauge you would get if worked in a single layer.