To DIY these kinds of dryer balls:
- Buy one skein (package) of 100% wool yarn at a craft store. This will cost you something in the vicinity of $5. (Fisherman’s Wool (US) works well. Note that major craft stores, at least here, have frequent 40%-50% off sales and accept competitors’ coupons.)
- Wind the yarn around a tennis ball until the tennis ball is completely covered.
- Trim end, then tuck it under a layer of wool so that it stays put. Tie a knot to keep it there.
- Throw the balls into the washing machine with some towels or linens and only a smidgen of detergent. When the washer is done, you may now throw the dryer balls into the dryer. The surface should be turned to felt.
A good-sized skein of yarn should yield something in the area of 3-4 tennis balls’ worth of winding.
I would not recommend doing this with the other kind of balls you folk seem to be talking about, though. They might not last if you put them in the washer.
