The Art and Science of Planned Pooling
By Karla Stuebing
What happens when knitting inspiration meets scientific method? A rare thing of pure beauty. Inspired by a pattern she found in an online knitting magazine, Karla Stuebing paired the mathematical expertise she uses as a statistical methodologist and research professor in the Department of Psychology at the University of Houston with her passion for yarn and needles. The result—a technique that's been dubbed planned pooling—is awe-inspiring. Here's a look at how she does it—and how you can too.
My fascination with pooling began in 2009 with a pattern called Sweet Spot, designed by Wannietta Prescod. Like so many knitters I had worked with variegated yarns for years, but it wasn't until then that I realized that the colors in variegated yarn repeat— apparently with great regularity. Inspired, I set out to adapt Wanietta's "recipe" to produce my own argyle pattern, using the same yarns, needle sizes, number of stitches, and the "knit-one-below" stitch (adapted from the book of the same name) that she used in her scarf design. I had mediocre success with this exercise and concluded that there was a great deal of individual variation across knitters. If I was going to find the "sweet spot" in a wide variety of yarns, I would have to come up with a technique of my own. Armed with variegated yarns from my stash and a few picked up at craft stores, I began to swatch, desperate to find the number of stitches required to get different patterns. I found that with regularity of tension and a yarn with a regular colorway (and, even better, one with nice distinct transitions between colors), patterns would show up at different numbers of stitches. As I endlessly knit my way through different stitch counts it occurred to me that the process I used in my work as a statistical methodologist would allow me to eliminate most of the tedious swatching.
What I realized was that there was underlying structure in the dye patterns of the yarns that wasn't immediately apparent when the yarn was skeined to feature the mixture of colors, rather than the pattern. I started thinking of the yarn as an unsorted spreadsheet or dataset. Through analysis, regularities can be found that are not readily apparent when just looking at raw data. So I decided to create my own data from the yarn, casting on fifty or so stitches and then knitting, all the while keeping track of the number of stitches I got for each color segment. For example, in a color sequence that was red, green, blue, I would note the following:
With this information in hand, I simulated a "virtual" skein of yarn with a computer program that I wrote using my statistical software and plotted it out the way it would look at many different stitch counts with different stitches: garter, stockinette, and with knit one below. I also wrote programs to simulate the patterns that would be found with knitting in the round versus knitting back and forth. In statistics, simulation is used in cases when we need to try something out before going to the expense of collecting data on real people. We also frequently plot out data to see the inherent structure or pattern that would not be accessible in any other way. For me, creating simulated yarn and plotting it out to see what it would do was the most natural thing in the world. It's how I work every day.
The following examples show the pattern you would expect to see for the red, green, blue colorway above, knitted out at two different stitch counts.
It quickly became apparent that when the stitch count was exactly consistent with the color pattern repeat (in this case 51 stitches or a multiple of 51), stacks of color like the first example above, based on 102 stitches, would appear. Multiples of the perfect stitch count plus or minus one or two stitches resulted in the most distinct plaid or argyle. Stitch counts between 51 and 102 provided a wide variety of intermediate patterns some of which are interesting and some of which are not.
As I worked all this out the cause of the mysterious shifting pooling patterns that show up on so many hand knit garments became clear. Slight changes in needle size, number of stitches, or even the tension of the yarn could have a profound influence on the appearance of the knitted fabric.
Taming Tension and Pattern Shifting
I spent two years swatching and honing my techniques for both maintaining a very regular tension (when that was desired) and for adjusting tension tighter and looser (on the same needles) when that was what was required to move the colors the way I wanted them to go.
In the shrug pictured above, I used a stitch count that was perfect for an argyle (about one to two stitches off of a perfect stack), and then loosened up for the portions where I wanted the pattern to stack instead of shift. This shrug is knit as a rectangle, from cuff to cuff.
Once I learned how to regularly pool in argyles, a friend asked, "Well, what else can you do? Can you do checks?" My first instinct was to tell him that that checks were impossible but then I started contemplating ways to create them. I realized that by using a stitch count that gives a perfect stack, and then breaking the yarn and shifting where to start in the color sequence could produce the results I was after. In the swatch below I started in the middle of the yellow segment for the first 20 rows, broke off the yarn and started knitting in the middle of peach segment for the next 20 rows, and so forth. Because I used two colorways that were similarly dyed, the pattern continued when I switched to the blue and brown yarn.
Three years after "inventing" this shifting technique, I picked up a book that contained a tiny little section on Ikat dying. As I read I realized that the shifting approach I was using in my knits is the same as that used to create Ikat weft weaving patterns. Nothing new under the sun!
Planned Pooling in Practice
Combining Colorways: Moody Blues Scarf
This scarf uses two different colorways of Blue Moons Fiber Arts Socks that Rock: Moody Blues and Blue Brick Wall. Because the original skeins are the same size, both colorways will stack at the same number of stitches. This scarf is knit sideways with a cast-on of about 250 stitches. I alternated 10 rows of each colorway and was delighted by the beautiful optical effects as the colorways take turns becoming figure and ground. The challenge of knitting a planned pooling project that uses a multiple of the perfect stacking number is that you have to keep the tension consistent across three repeats of the color, hoping to come out at the end of the row right where you want it to be. I used the lessons learned from my shifting swatch above to produce this piece where I had to break off the yarn for each colorway and start it again at the right spot after ten rows of the second colorway. Carrying it up the side is not an option because you end up with the color sequence starting in a new place and that spoils the effect of the alternating bands of colors. If I were to do a piece like this again, I would plan to leave the cut ends exposed as part of the design, either knotting and adding a bead to each join or braiding the ends along with additional lengths of yarn.
Variations On a Rectangle: Ruffle-edged Cowl
We've seen that a skein of a given size will stack or argyle on a very specific number of stitches. I wondered what the alternatives might be if you wanted a scarf, for example, that was not the width dictated by the length of the color repeat. One solution I hit upon was using short row edges, where I knit out to the end, turned back and knit about six stitches, knit back out to the end of the row and then all the way back to the other side. In each row, the same number of stitches was used, maintaining the positioning of the color repeat, but the width was narrower because the ends were knit back and forth twice. The short scarf/cowl below was made in Prism Yarns Merino Mia in the Alpine colorway.
Bias and Combining Colorways: Wing Shawl
I used a bias technique to make a non-rectangular shawl from two colorways (Edgewater and Sea Side) of Lorna's Laces Shepherd's Worsted Multi. The two colorways were alternated in blocks. I increased one at the beginning of each odd row and decreased one at the end of the same row. The return row was knit without changing the number of stitches. This produced a parallelogram-shaped wing for one side of the wrap. When one side was long enough, I knit the center back block straight with no shaping and then reversed the shaping to create the other wing, decreasing one at the beginning of the row and increasing one at the end. I used the skills I had learned on the Moody Blues scarf to help me find the right starting place for each yarn as I picked it up again.
Knitting Back and Forth In the Round: Argyle Socks
My friend and co-moderator of the pooled knits group on Ravelry, Gladys We, challenged me to figure out how to do an "argyle" sock using planned pooling techniques. The problem is that to get the crossing of colors required for an argyle, you have to knit back and forth. I found a solution that I like when I read an article about a sliding loop join in intarsia knitting. I knit the stocking on double-pointed needles on the number of stitches required to get an argyle, but after completing the first row, instead of spiraling around, I pull up a long loop of yarn through the edge of the next stitch to join and then purl back, using that loop of yarn until I reach the end of the row again. I then tighten up the remaining slack yarn, pull up a loop again through the edge of the next stitch and then knit back around using the yarn from that loop. You are essentially knitting back and forth but joining at the end of each row. In order to avoid disrupting the design with a gusset, I planned for an afterthought heel. As you can see in this photo, the symmetric dye pattern of this colorway, Crazy Lace Agate from Blue Moon Fiber Arts, allows for continuation of the pattern even across the join at the back of the sock.
Karla Stuebing is a statistical methodologist and research professor in the Department of Psychology at the University of Houston. She invites Twist readers to take the planned pooling plunge by joining her in the Pooled Knits group on Ravelry, co-moderated by Gladys We.