Unfold the the socks before placing them in the washing machine. The top of each sock tends to roll under when taken off. Folded and rolled socks can't come completely clean during washing, which can result in a hard texture.
Place the socks in the washer, taking care not to overfill the wash tub with too much clothing. Over-filled tubs can't agitate and clean the clothing properly.
Set the washer on the normal cycle. Use warm or hot water.
Add the detergent to the wash tub after it fills with water. Then add 1/4 cup baking soda to the water. The soda helps break down any soil that could cause hardening in the socks and clothing.
Open the machine before the final rinse cycle. Add 1/2 cup of plain white vinegar to the rinse water. The vinegar ensures all detergent and any hard water residue is removed from the socks.
Place the freshly washed socks into the dryer, and tumble dry. Add a fabric softener sheet to further ensure the socks don't become hard. Or hang them on a line and air-dry, if you prefer, although they won't get as soft with this drying method.