Unfortunately I didn't take photos of the steps as I went (I hate taking pictures at night in artificial light or with the flash), but the process was simple enough that I think I can explain it pretty well using the "after" photos below.
-I started with a 100% wool pullover that had been slightly shrunken and a bit felted in the wash (woops). Find the exact center of your sweater at the neck, then follow the row of knitting and place a series of pins vertically down the entire front to show you where to cut.
-Carefully cut the sweater open along your marked line, pulling out pins as you go.
-Next you'll need enough grosgrain ribbon for each open side, plus a little. Decide which side you want the buttons to be on (ladies' tops usually have the buttons on the left when the garment is on, so on the right when it's laying on the table facing you).
-(I started with the button hole side of the sweater.) Lay your ribbon along the outside edge of the sweater, matching your edges evenly and leaving about an inch of extra ribbon at the top and bottom of the sweater.
-Fold down the excess so that your fold is even with the top and bottom edges of the sweater.
-Pin the length of ribbon to the sweater.
-Stitch along the edge using a 1/8" seam allowance. Reinforce your stitching at the beginning and end of the ribbon.
-Turn the ribbon to the inside of the sweater and press your seam.
-Pin the turned ribbon down (the folded raw ends of the ribbon should now be underneath itself) and stitch along the inside edge of the ribbon, as well as along the top and bottom edges. On this step I sewed with the sweater facing up so I could follow a row of knitting to make a nice straight line of stitching. Just be sure that the row you choose to follow will catch your ribbon underneath all the way down.
-For the other side of the sweater simply match the edge of the ribbon with the edge of the sweater as before, but this time fold your excess ribbon under itself, so the raw ends of the ribbon are hidden.
-Stitch along the very edge, and when you come to the bottom just turn and stitch down the fold, then stitch your way back up the other side of the ribbon, again on the very edge. Stitch down the top fold as well.In this photo you can see that the ribbon hides the raw edge of the sweater nicely, and because it's slightly felted it won't unravel.
- You can now choose the type of closure you'd like to use- buttons and holes, toggles, frog closures, etc. and add them to each side of the sweater. I decided to go with one strategically placed button and a thin loop of leather for mine. This keeps the cardigan closed, allows easy on and off, and gives me plenty of room for my growing belly. After my pregnancy I may go back and put buttons and holes along the entire length, but I kinda like the way it is for now.
I secured the leather with just a couple of rows of stitching...
...and a chunky button stitched to the ribbon on the other side completes this simple closure.
I'm thinking I'm gonna get a lot of use out of this new sweater. I never wore it much before because the wool was just a bit itchy on my neck, but now that the neck can fold down it's just right for throwing on over a tee shirt. This project would be really cute with a full turtleneck sweater as well, giving you a nice big shawl collar. Hmmm... do I have any wool turtlenecks I wanna cut open? Ooo! You could also try cutting the opening off to one side like those chic assymetrical cardigans I've seen- love that!!
Anyway, if you decide to try this let me know if you have any questions. I realize my "tutorial" may have been a bit confusing. Hope it turns out for ya!