Fill the washing machine with cool water.
Add the appropriate amount of laundry detergent to the water while the machine is filling.
Put the pillowcases in the washing machine. Wash your satin sheets at the same time, if you wish.
Close the lid, and let the wash cycle proceed to the final rinse.
Add fabric softener to the wash during the final rinse. This will help keep the satin supple. Close the lid, and let the cycle finish.
Put the pillowcases in a dryer on a no-heat cycle until they are completely dry. Alternatively, you can hang them on a line to air-dry.