First, I chose the method of cut open and trim that I wanted to use. I chose the sandwich steek (as described by Kate Davies) because it makes a very nice neat finish. I chose a silk yarn and, because I wanted to see how it knitted up and to check the gauge, knitted a little sample. I was then able to count the stitches per 5cm, and decide how many rows the trim should be.
I then used the sewing machine to stitch two lines, parallel to the centre point that I had marked earlier.
Then, I cut close to the stitching.
Next, I calculated how to pick up the stitches, using the cut open and trim advice. The old rows per 10cm (in my existing fabric) was 82r. The new stitches per 10cm (in my new fabric) was 21st. This gave a multiplier of 0.26. I chose the nearest option in the pick up spacing table: 0.25. This told me to pick up one stitch for every 4 rows in the old fabric.
I used a fine (1.3mm) crochet hook to pull the yarn through the fabric, picking up a few stitches in from the sewing. Even though it was a reasonably thick yarn, and stranded, I managed to get it through without too much trouble. As I pulled each stitch through, I put it on a circular needle.
When I did the second side, I was careful to make sure I picked up exactly the same number of stitches. I purposely did the left side first, so I could place the buttons and decide how many to use before working the buttonholes on the right side.
I worked out how to space the buttonholes evenly, and used a one-row buttonhole (as described in The Handknitter's Handbook, p196).
I chose to work the first row of the sandwich as a purl row, to get a garter edge. I was very pleased with how it turned out!
It's neat on the back, too - the raw edge is firmly secured.
I was very pleased with my cardiganisation! I think that I feel particularly fond of it, because both the yarn and buttons have nice memories associated with them. I bought the silk yarn from a lovely yarn shop in Berlin last summer, and the buttons are left over from my degree collection. I remember going to have them dyed by a nice man in a dingy warehouse somewhere in the backstreets of Salford!
Check out the previous step: afterthought pocket.