Your gauge isn’t the same when you are knitting in-the-round and when you are knitting flat. Period. So if you base your maths on a swatch that is knitted flat to decide how many stitches to cast on for your knit-in-the-round, you’re heading straight into disaster. The same is true of the reverse.
A frequently used method of getting around this obstacle is to knit a swatch flat, but modifying the technique to make it look more like you are knitting in the round : what you do is that you use the same technique as the i-cord (with far more stitches of course!) and you carry your thread on the back of the knit in a very (emphasize on very) loose way. The gauge you get is pretty much the actual gauge you get when knitting in-the-round.
I, however, don’t like this method. Why go for the fake thing when you can get the true one ? Also, I like doing colourwork and good patterns indicate which gauge you should have whilst knitting the colourwork in-the-round. The fake method gets real messy with all those floats. Also, as you will later see, I like to reuse my swatches for all sorts of stuff and a swatch that is full of loose floats on the back of it is just not my idea of fun. So, what do I do ? Simple, I use steeks.
Once thus secured, I cut my swatch between these two lines.
Steeks are widely used in traditional Scandinavian knitting. You are knitting in the round (often in colourwork) and you are knitting a few stitches in the same colour each round and these stitches is where you intend to cut the knit to create openings (for your arms, for instance). Thus when I am created a swatch for a knit in-the-round, I simply knit in the round using less stitches than the real things but still enough in order to have a swatch that has a circumference of about 15cm /6 inches (I prefer larger swatches, but you do you). I go on knitting in the round until I have about 13 cm /5 inches in total and I bind it off. Than I select 3-4 columns of stitches and these stitches, I decide, will be my steeks.
I will be cutting through the middle of this column of stitches. Now, if I am using traditional Norwegian wool, I don’t need to do anything special, I can start my cutting straight away and my only concern is that I find scissors sharp enough to cut through that sturdy wool. But that isn’t the most common situation, is it ? The most common situation is that you are knitting a swatch made of merino wool, or cotton, or whatever and if you just cut you knit vertically, the whole thing will unravel. Before grabbing your cissors, you need to secure those columns of stitches that will become your sides of your flat knit. Because this is the whole purpose of using steeks : you end up having a flat swatch that is easy to measure but that also is your authentic gauge when knitting in-the-round.
How to secure these sides ?The way I do it (when the wool isn’t all that slippery, when it’s alpaca or merino, for instance) is that I use a simple back stitch seam, using a wool that is not quite as thick as the one I am knitting with. I am going through each little bar in the middle of every single stitch that constitutes that column and I do the same in another column. two or more stitches away. Once this is done, I cut my knit through the middle then proceed to go and soak it before blocking and measuring my gauge.
This way of securing my steeks is NOT the way you would usually do it. I do it because it’s quick and convenient. And I just need a flat swatch, not something that can go through multiple washings and wears as for a garment. But when I have to swatch in-the-round something that is very slippery I don’t use my back stitch short cut as it wouldn’t work. I find the most secure and effective way to secure your steek hedge is to use a crochet and work a vertical slip stitch line or a single crochet one. Again, I am working through the little bar at the center of every single stitch. For this I use a crochet that is at least one size smaller than the size of the knitting needles I am using. Two sizes smaller is better. Importantly, I am not using the same yarn as the one I am using for the knit : I am using a yarn that is thinner. I use whatever scrap yarn I have, but not a yarn that tends to split. Yarn that splits is annoying to work with and I find it confusing because I can’t remember where I’m at. As long as your wool is thinner and your crochet hook is smaller than your knitting needle, you’re good to go. Your crochet doesn’t need to look good. Once it’s done, there you are, you grab your scissors and cut.
There’s plenty of videos out there demonstrating how to use steeks, how to secure the sides of your steeks before cutting them and how to create a fake knit-in-the-round gauge swatch. What I haven’t come across, so far, is a video or a text instructing you to use steeks for creating a real knitted-in-the-round swatch. I don’t understand why. So should you choose to trust me and follow my example, I think it fair to warn you that this is a rather solitary path.
If you are an advanced knitter and have good reasons to think that the method I suggest is not as good as the usual fake one I described on top of this post, I’d be very interested in reading your comment. Likewise, the fact that I have never came accross videos or texts using my steeks method is in no way an indication that this method of dealing with such swatches is uncommon. I only speak French, English and German. The internet is vast and those three languages are not the only ones spoken in the knitting community. Colourwork is an important part of all North Atlantic countries as wall as the Baltic States. I’d be interested to learn how these knitting cultures deal with swatches for items knitted-in-the-round.
Unsolicited Knitting Advice 