If you've ever knit through the back loop of a knitting stitch, you probably know that it produces a twisted stitch. Though it is less common to do so, the same thing can be accomplished from the wrong side of a knitting project—or wherever a purl stitch falls—by a move known as purling through the back loop.
In knitting patterns, you'll see this special stitch "p1 tbl" or "Ptbl." The directions may also say "purl into the back of the stitch," and, if you follow knitting expert Barbara G. Walker, you'll see it as "p1-b." No matter what it's called, the stitch is a bit awkward but easy and it will give your stitch the desired twist.
How to Purl Through the Back Loop
Doing a purl through the back loop is a little more fiddly than knitting through the back loop. It is not difficult to perform once you've tried it a couple of times.
When purling in the normal way, you work with the front part of the stitch—the part that is facing you and closest to you on the needle. When you purl through the back loop, you do exactly the same steps as regular purling, but you work with the part of the loop that is on the back of the needle.
The key to doing this properly is to make sure you're entering the back of the stitch from left to right when working the stitch to get the right twist.
You'll also sometimes see instructions that indicate going through the stitch from right to left. This will still make a twist, but many knitters find it even more awkward than the other method. As long as you're consistent, it doesn't matter which technique you use.
Stitch Patterns Using P1 TBL
Purling through the back loop produces a twisted stitch and it is commonly used in the twisted stockinette stitch.
There's also a variation of single ribbing found in Barbara G. Walker's "A Treasury of Knitting Patterns" that relies on back loop stitches. It involves knitting the knits through the back loop on the right side and purling the purls through the back loop on the wrong side throughout the pattern. You can see a picture of this stitch in action on the Walker Treasury website.
To write that in knitting language (works on an even number of stitches):
- Row 1: *K1 tbl, p1. Repeat from * across. (This is the right side.)
- Row 2: *K1, p1 tbl. Repeat from * across.
- Repeat these 2 rows for pattern.
Another Walker Treasury stitch that uses p1 tbl is called the Twisted Check. This one uses both knit and purl stitches worked in the back loops to make a sort of tweedy textured pattern.
Here's how that one goes (requires an odd number of stitches):
- Row 1: K every stitch through the back loop.
- Rows 2 and 4: *K1, p1 tbl. Repeat from *, end k1.
- Row 3: *P1, k1 tbl. Repeat from *, end p1.
- Row 5: Repeat row 1.
- Row 6: *P1 tbl, k1. Repeat from *, end p1 tbl.
- Row 7: *K1 tbl, p1. Repeat from *, end k1 tbl.
- Row 8: Repeat row 6.
- Repeat these 8 rows for the pattern.
Twists Tighten Things Up
Using twisted stitches makes the fabric tighter. If you're working a pattern that uses a lot of twisted stitches, your gauge can be quite different from plain stockinette. Make sure you always do a gauge swatch when working such a stitch pattern so you can make adjustments before diving into the project. You can also try working any pattern with twisted stitches on larger than called for needles.