Felting (or fulling) is the process of using hot water, agitation, and suds to change (or shrink) a knitted piece into a felted fabric that will not unravel, even when cut. Felting creates a very durable fabric that is practical as well as beautiful.
When making an item to be felted, use extra-large needles and make it several sizes larger than normal. This creates space between the stitches and rows and allows the fibers to shrink while maintaining a smooth fabric surface.
Animal fibers are best for felting. You can use wool, mohair, camel, and alpaca, among others. Superwash wool yarns have been treated to resist shrinking -- they will not felt. Synthetic yarns do not felt, either.
To felt, set the washing machine on the hot water cycle and low water level. Add a small amount of dishwashing liquid; too many suds hampers the felting process. Add towels, tennis balls, or washable sneakers to the machine to balance the load and aid the felting process. Allow the machine to agitate for five minutes, then stop it to check the amount of felting. Continue to check every five minutes or so until the stitches completely disappear and the item is the desired size. The amount of felting time varies depending upon yarn, washing machine, and hardness of water.
Once the desired felting stage is obtained, remove the item from the washing machine, drain the soapy water, and fill it with cold rinse water. Soak the item in rinse water for several minutes to remove all soapiness. Set the machine directly on spin cycle to eliminate excess water from the felted item, or wrap it in a large towel and squeeze to take out the rinse water. Remove the felted item from the machine immediately after spinning to avoid wrinkling the fabric. Stretch, pull, and pat it into shape, and allow it to air-dry on a flat surface.
In the last section, you'll find a handy chart for deciphering all those knitting abbreviations.