Blocking Cowls
How you block a cowl depends on the supplies you have and the kind of cowl you’re blocking.
Knit Flat and Grafted
Cowls that are knit flat and grafted can be blocked before or after joining.
To block a cowl flat before you graft, optionally place a lifeline through any live stitches and transfer them to a blocking wire. Soak and block the piece as you would a wrap or scarf. When it has dried, return the live stitches to your needles and join as instructed. You may want to reblock the join, depending on how different it looks from the rest of the piece once completed.
Knit in the Round
I use two different methods for blocking cowls that are worked in the round, depending on the results I want. Both methods eliminate the creasing that occurs when you simply block a cowl flat.
Method 1:
The first method maximizes circumference but is not as good for dealing with non-straight edges (such as picots or points). In the photos below, I used four blocking wires, blocking mats, pins, and three rolled bath towels.
To use this approach, optionally run a blocking wire through both sides of the top and bottom openings of the cowl (four total), leaving about 3-4 inches between where one wire stopped and the other began so that the cowl can curve around the towels. This step isn't essential, but it achieve nice, straight edges.
Lay the cowl out so that the top and bottom edges (and their wires, if you’re using them) are parallel.
Now add the towels (or something similar, like foam rollers): Roll two bath towels (blue in the photos), then tuck one through each side of the cowl (where there’s no blocking wire, if you used them). Optionally, roll your third towel (purple in the photos) crosswise under the whole cowl and the other two towels, which just helps get more airflow to the side of the cowl that is pressed against the mat. Once the towels are in place, push the towels along the sides (blue) outward until they pull the stitches tight. As you can see in the first photo, they are slightly closer together at the top than at the bottom, which reflects the shape of this particular cowl (Willowfall).
Finally, add the pins: The towels will hold the sides out, but you’ll want to pin the edges (with or without wires) into place, either into the mat or into the towel. Tip: Because the towel isn't as firm as a mat, stick the pins in at a steep angle, pointing sharply toward the cowl with the head aiming away, to minimize how much they can slip. Allow it to dry completely.
This method can also be used for bandana-style cowls that come to a point in the front (such as Escherite). Just pull the front point out and pin it into place, optionally with a blocking wire run through each half and crossing at the point. Thanks to YogaKnitra666 for the photo (via Ravelry).
Method 2:
The second method maximizes height and is great for pinning out fancy edges, but you tend to lose some of the circumference around the middle. I learned it from Hunter Hammerstein. In the photos below, I used two straight blocking wires, two flexible blocking wires, blocking mats, pins, and something on which to rest the cowl (in my case, two tubs of cashews!).
To use this approach, run flexible blocking wires (or something similar) through the top and bottom of the cowl. If your piece has picots or points, be sure to run the wire through just the end of each point (as pictured). Overlap the ends in order to keep them from pulling the spot where they cross out of shape. Run your straight blocking wires (or something similar) through the top edge of the cowl at right angles to one another so that they form an X in the middle.
Next, find something to from which to suspend the cowl. It should be tall enough to get the blocked height you want while still leaving enough space for you to pin the bottom edge to the mat. Lower the cowl down over your chosen support until the wire X comes to rest.
Adjust the top edge by pulling or pushing the wires until the circumference is to your liking. Do the same with the bottom edge, then pin it in place on the mat if necessary. Allow it to dry completely.