Believe it or not, sometimes people do this on purpose. According to Knitting: Fashion, Industry, Craft
some hats were made by knitting fabric pieces, felting the piece, then cutting out the shapes and sewing them together.
I've done a few samples, but this was my first finished project: the bag is knitted complete then felted (I've found the "sanitize" cycle on my front-load machine works great). After felting the bag is about 20% smaller, and the fabric is very sturdy and dense.
|closeup of wool fiber|
Those scales work like a cable tie--you know those plastic straps that you can pull tighter, but can't loosen? All those fibers criss-crossing keep getting pulled tighter, making the overall dimensions smaller, but the fabric itself thicker.
Washable wool doesn't do this because its been treated--either to coat the edges of the scales or to etch them away.
Pretty cool, huh?
yeah, I'm a fiber nerd, and dang proud of it. :)