Anna: I managed to cobble together leftover bits of yarn to make 2 test swatches of my sweater. This evening, I tried blocking them.
There are three recommended methods to block crochet. The yarn I chose for my sweater is 100% acrylic - I picked it partly because it's machine washable and drier safe. When I blocked the panels before putting them together, I used the method recommended for acrylic. The dry pieces were pinned out, then I sprayed them with water and left them overnight to dry. I rarely need to block things, and this is not the method I normally use.
Before: Here are the two swatches, ready and waiting to be blocked. I didn't bother sewing in the yarn ends, so you can see some of the places where I joined new ends. I had to use 5 left over pieces to make these. *L*
Method one: Maiming - this is my usual method of blocking. I completely soaked the piece, squeezed it dry in a towel, then pinned it out, stretching the swatch out to the shape I wanted (the middle wants to pull inwards, making an hourglass shape, unless it's pinned out).
Method two: Killing - after pinning the dry swatch to the surface, I used my iron at highest heat and steamed the heck out of the swatch, while being careful not to actually touch it. This method is NOT normally recommended for acrylics.
(And since I was blocking things anyways, I pinned out a round doily-type mat I'd made, too. For that, I wet it and pinned it down, like the previous swatch.)
After: Both swatches look pretty much the same at this point. Steaming didn't get it as soaking wet as the previous swatch, of course. Now, they sit overnight to dry.
Based on what I've read, the steam method leaves acrylic fibers with a lot more drape than the other methods. Since all methods the methods permanently effect the yarn, I don't want to take any chances.
I do wonder, though, how I'd go about steaming the entire sweater. It's quite large. Whichever method I end up using, I'll have to use one of our futons to pin it to. Holding a steaming iron over all that surface until it's wet will be a challenge! *L*
While I'm figuring all this out, I've started on my daughter's coat.