Let’s start with the good news: gauge isn’t critical for Aurora. If you want to get started and see if you’re happy with the fabric you’re getting and adjust needles in the early stages of knitting, this is an option. The pattern contains notes on how to weigh yarn as you go to ensure that you’ll have enough left to finish the pattern and support this approach.
However, if you do want to get gauge, here’s how I’d recommend swatching for Aurora.
Use the i-cord cast on as per the pattern instructions. Knit so you have 30 stitches to pick up along the i-cord edge before unravelling the provisional cast on. With the i-cord edging on both sides, you’ll have a total of 36 stitches for your swatch.
Go to the brioche increase section and follow rows SU1-SU6 in the pattern. This doesn’t actually get to the increase rows, so you’re creating a straight brioche section in two colour brioche. After knitting these rows once, continue knitting rows SU3-SU6 to continue producing a straight brioche section. I would repeat SU3-SU6 12 more times after the first time you knit SU1-SU6.
Once you’re done with that, you’re going to skip ahead to the bind off section in the pattern and use the i-cord bind off instructions that are written there. You should be on the right side, but use whatever colour suits you – don’t worry about the colour in the bind off section on the pattern. Given it’s a swatch, it’s up to you whether or not you can be bothered kitchener stitching the i-cord together (it could help improve the quality of your measurement a bit) or simply bind these stitches off.
After getting your swatch off the needles, you need to soak and block it. I’d pin it out fairly hard like you would with the finished shawl and let it dry completely. Once it’s dry, unpin it and lay it on a flat surface to measure it. The blocking is important, because my gauge measurements are taken after I blocked my shawl under tension and opened the fabric up – it made a huge change to the drape of the finished item.
I have two gauge sets below, because I used different yarn bases for the two colour and three colour shawl. These are both measured across 10cm.
Brioche is hard to measure, because it’s such a fluffy and malleable stitch. This is why both the pattern and the swatch have an i-cord edging – to help it hold its shape. I laid it out on a flat surface, smoothed it out, and let it lay naturally and I tried not to rearrange it as I measured. I found I could easily change the results by scrunching the fabric up or pushing it out very slightly without apparently distorting it. I have done my utmost to get good measurements! The swatch should be big enough to let you measure from the middle of the swatch with a bit of room to spare on either side stitch and row-wise.
How to count stitches and rows in the swatch
To count the stitches, you want to count the “v” rows created by the brioche knit stitches in the main colour and the other colour purl bumps between them. In the photo above, the brioche knit stitches in the dark colour count as 1 stitch and the space between them in the turquoise count as 1 stitch.
To count the rows, you want to count each “v” created by the brioche knit stitch as a row. As the pattern is written, you’ll actually only create 2 of these each time you work SU3-SU6. This is because each row of brioche is worked twice, once in each colour. So that’s why it feels like you’ve worked way more rows than you see when counting your gauge – each row works only half the stitches.
Across 10cm, I had 20 stitches and 21 rows in two-colour straight brioche stitch after blocking hard.
Across 10cm, I had 22 stitches and 19 rows in three colour straight brioche stitch after blocking hard.
The pattern isn’t sensitive, has tips about weighing and brioche is hard to measure; so if you are getting anywhere between 18-22 rows and 19-23 stitches, I would recommend getting started with those needles and keeping an eye on weight to track yarn usage!