Updated: Mar 10, 2022
Are you pinning your swatches?
You’ve dutifully cast on and knit a generous swatch. You soak it, squeeze it, and lay it flat. Then, you pull out your pins.
Put the pins away!
Letting your swatch dry on its own will allow it to shift and settle into its accurate gauge. If you base your gauge on a stretched swatch, the first time you wash your sweater you may be unpleasantly surprised. If your pins have distorted your swatch gauge, your project may be either broader and shorter than anticipated - or narrower and longer. Pinning might also obscure something important about the fiber, like a bias twist, below.
Instead, put your swatch on a flat surface and gently pat it into shape. The soaking and squeezing process may have stretched the swatch some, so I like to pat it in a few directions to see how it lays the most naturally. Let your swatch dry - then let it sit for at least 12 more hours. Wool, especially, has a lot of bounce - giving the yarn that extra time to return to itself will create the most honest swatch.
Superwash yarn stretches when wet - a lot
If you've ever been unpleasantly surprised by what happened to your freshly washed superwash sweater, which now reaches your knees, this same principle may be at work.
A swatch is generally not very heavy, so there isn’t much distortion in a superwash swatch. Once you soak a whole sweater or piece of a garment, however, those sleeves can start to look like scarves as the water weight stretches the fabric. If you don't account for the stretching that takes place during soaking and squeezing, you will unnaturally distort your sweater.
Superwash likes to be patted gently back into a gauge that more closely resembles its working gauge (the gauge you’ll see when you’re working your swatch). When I’m blocking or laundering a superwash project, I find that it often looks positively rippled with extra volume as I tuck it into the dimensions I’m expecting. Returning a day later, the yarn has dried flat and smooth, with plump stitches that don’t look strained in any direction.
Treat your swatch well, and let it tell you how to care for your sweater
So there’s some nuance here - you want your swatch to predict what will happen when you wash your sweater, but you don’t want to plan for a permanently distorted sweater, either. By paying attention to your working gauge, treating your swatch tenderly, and allowing the yarn to do its thing, your swatch will tell you not only what gauge is, but what to expect when blocking and laundering tricky fibers.
Check out Ysolda's book Little Red in the Big City for a beautiful discussion on gauge. This book is an incredible resource for making sweaters that truly fit, and I love that she educates from fiber through construction.
Brooklyn Tweed has a fantastic article on swatching, which you can read here.
I find swatching to be a creative practice on its own and frequently create swatches just to see how fiber works up or what a stitch pattern will do. For inspiration, check out Norah Gaughan's book Knitted Cable Sourcebook.