Day 14: What’s the worst yarn/fiber that you’ve worked with and why?

Baby Monkey Yarn. Don't get me wrong, it is the softest most wonderful feeling yarn I've ever used. Knitting it may have been okay. But crocheting it using a dark colour? Forget about it. I couldn't tell where my stitches were so what I made from it turned out to be not the shape I wanted. I'm pretty sure knitting it would have been fine, unless a stitch was dropped.