I first saw this tip on page 141 of Maggie Righetti’s Sweater Design in Plain English (New York: St. Martin’s, 1990).
It’s also on TechKnitter’s blog.
The genius of these methods is that they will survive whatever technique you use for blocking the swatch.
If You Make an Individual Swatch for Each Needle Size
This technique will work for any fabric, from garter and stockinette to very complicated patterns.
Leave a longish cast-on tail, and tie a series of simple overhand knots in it, with the number of knots matching the needle size.
Size 5 for this swatch? Tie five overhand knots in the cast-on tail. Size 7 for that one? Use seven knots.
If you use metric needle sizes, then you’ll have to deal with half and even quarter millimeters. For 3.25 mm needles, you could do three knots very close together for the number of whole millimeters, with a fourth knot a little way away to represent the quarter millimeter. For 3.50 mm, you could do two groups: one with three knots close together plus a group of two (one for each quarter of a millimeter) far enough away that the knots don’t look like a single group of five. (And you’ll have to be consistent about which group is closest to the swatch and which is closest to the free end of the tail.)
If you frequently use the smaller metric-size needles, which go in 0.25 mm increments from 2.00 to 4.00, you could also just make a cheat sheet for yourself:
- 1 knot = 2.00 mm
- 2 knots = 2.25 mm
- 3 knots = 2.50 mm
- 4 knots = 2.75 mm
- 5 knots = 3.00 mm
- 6 knots = 3.25 mm
- 7 knots = 3.50 mm
- 8 knots = 3.75 mm
- 9 knots = 4.00 mm
There would probably be no possibility of confusing two swatches that both have nine knots in their cast-on tails, one made on 4.00 mm needles and the other made on 9.00 mm needles, since the size of the stitches would be so obviously different.
If You Make a Continuous Swatch
This technique works best in garter and stockinette, but it can be done in a more complicated fabric too.
As you switch needle sizes every three or four inches, work the needle size into each section of the swatch with purl bumps and/or yarnovers.
Use yarnovers, because purl bumps won’t show up. A row or two after you switch needle sizes, or even in the same row if you’re afraid you’ll forget (I would get distracted and forget, for sure), work several “yarnover, knit two together” pairs so that the number of yarnovers matches the needle size.
If you’re working with those smaller metric needles, then either use the cheat sheet shown above, or do two groups, one group for the number of whole millimeters and a second for the number of quarter millimeters (so for 3.75 mm needles, do two well-separated groups that each have three yarnovers).
Make a purl ridge (knit a row on the wrong side of stockinette) where you change needles, then two or three rows above it, work purl stitches on the knit side, matching the number of purls to the needle size. Six purl bumps mean a size 6 needle.
If you’re using metric needles smaller than 4.00 mm, then do the same thing, but add a “yarnover/knit two together” pair for each quarter of a millimeter. For 2.75 mm needles, work two purl bumps and three instances of “yarnover, knit two together.”
Using knots in the cast-on tail works for individual swatches for each needle size in any pattern. But yarnovers work best for a continuous garter swatch, while purl bumps and/or yarnovers probably won’t work well in anything but a continuous stockinette swatch.
If you prefer to do a continuous swatch in any kind of patterned fabric, then work several rows of plain stockinette after each needle change, using the purl or yarnover techniques in the stockinette portions to record what size needle you switched to, then start working the pattern stitch again.
Yes, you’ll do several extra rows for each needle change, but sometimes it’s easier to compare different areas of a single swatch instead of comparing a bunch of individual swatches.