Two-colour brioche patterns typically start one of two ways: either you work a standard cast-on in a single colour, or use the two-colour Italian cast-on (as favoured by Queen of Brioche Nancy Marchant). This is a fast and easy cast-on, it sets your two-colour rib up right from the get go, and it's elastic to match the fabric. Beautiful choice.
Unfortunately I don't like how it looks. It's just a personal thing. I'm not a big fan of tubular cast-ons either, and I know I'm very much alone in that. I like a bit of structure to my edges, so for Wraparoche, I went looking for an alternative, and I found this beautiful technique that creates the effect of a chain of stitches in alternating colours.
It's definitely a decorative edge, rather than something that will blend in to the fabric – the colours can't be made to line up with the stitches in the first row, but will rather alternate (if used for a corrugated rib, brioche or similar stitch). And it's not stretchy, so take care to work it reasonably loosely to match the brioche fabric; if you tend to cast on tightly, go up a needle size or two.
Note: It is essential to always draw the active yarn forward on top of previous yarn. You will have to untwist them regularly, but this is what creates the braided effect.
1. Make a slipknot holding both yarns together. This will be pulled out later.
2. Insert RH needle between the two loops and draw FC yarn forward as for a cable-cast-on.
3. Insert LH needle into stitch FROM BEHIND – giving it a little twist.
4. Bring BC forward, ON TOP of FC, and repeat steps 2-3 using BC.
5. Repeat from step 2, always bringing active yarn forward on top of the previous yarn to create the “braid”.
6. When you have cast on the desired number of stitches, not including the slipknot, release the slipknot and pull it out.
I've been asked how you should join in the round using this technique. Covering joining in the round is a whole separate blog post really, but in brief: all I did for Wraparoche was to start in the round, pulling the yarn tight across the gap, and I used the starting tails to close the "braid" when finishing and weaving in ends. If you normally cast on an extra stitch and knit that together with the first stitch of Round 1, that works too. Crossing the first and last stitches over each other is not recommended, though, because that messes up your colour sequence.
Stay tuned for a tutorial on the two-colour brioche cast-off!