Step one...the core...I wound a ball of scrap acrylic until it was about 7 1/2-8 inches in circumference.
Step two...winding the wool...I chose to use Knit Picks Wool of the Andes, as if felts up so nicely, but you can use any non-superwash wool. Each ball takes about 50 yards. Wind the wool yarn snugly around the core ball so that all of the core is covered evenly.
Step Three...securing the tail...using a crochet hook, secure the tail under loops of yarn until there is no more hanging out.
Step Four...preparing for the first felting...tie the completed balls into a lingerie bag or a nylon stocking to keep them from unraveling, and toss in the washer, then the dryer.
Step Five...the second felting...remove the ball(s) from the lingerie bag or stocking, and wash and dry again (at this point they will NOT unravel!)
The ball on the right has been felted once, the ball on the left, twice.
At this point they do not really need to be felted anymore, but you can repeat step five as many times as you like.
Use in place of dryer sheets (which can diminish the life of you dryer, cause buildup on clothes...especially cloth diapers, or cause allergic reactions for some people). I ended up making 4 of these balls, and they work wonderfully. My clothes and cloth diapers are coming out of the wash fluffier and softer than ever! They work even better than the store-bought variety, and don't have the unpleasant rubber odor!
Another great felting wool is: