Apply stain remover to the sweater if necessary, following product instructions.
Turn the sweater inside out to prevent excessive pilling in the laundry or place sweater in a mesh laundry bag.
Set the washing machine to a cool cycle and add the sweater with other like colors.
Add your regular laundry detergent and start the wash cycle.
Remove your sweater from the washing machine.
Lay the sweater flat on a towel to dry, being careful to push or pull it into the desired shape as it dries. Turn it over to dry the other side when necessary. Keep your sweater out of direct sunlight and heat sources. Mark the outline of your sweater on the towel so you can check for shrinkage as it dries.
Iron your cotton sweater on the medium- or high-heat setting if desired after it is completely dry.