When getting a mystery yarn, you should always do a bleach or burn test to see what the yarn is so you know how to wash and block it. I burned a bit when I got this mystery purple yarn. I also didn't believe that the yarn was acrylic (who makes acrylic laceweight?) so wrote it down as wool. While not a problem for the knitting, it was a big problem when I unpinned it after blocking and it scrunched right back up to pretty much how it looked off the needles.
Now I need to re-pin it and use my iron to "kill" it into the shape I want. I just wish I realized before unpinning it all!